Audio only mode will be toggleable only from the VideoStatusLabel,
so remove AudioOnlyButton from the toolbar and delete the component
itself. As a result of the button being removed, a truthy check in
VideoStatusLabel was also removed to ensure it will display as it
is now the only way to toggle audio only mode. Also set the cursor
on VideoStatusLabel to always be default, so it can never show the
text cursor.

Add a menu that displays when hovering over VideoStatusLabel. The menu's
display is controlled by CSS. As the existing AudioOnlyLabel no longer needs
needs its own tooltip, it has been removed and label display logic has been
moved into VideoStatusLabel.

DialInNumbersForm has been modified to display a conference id to be used for
dialing into the conference. The changes include:
- Requesting the conference id and adding the conference id to the redux store
- Displaying the conference id in DialInNumbersForm
- Modifying the copy behavior to support copying the new message to clipboard
- DialInNumbersForm does not display until all ajax requests have completed
  successfully. This eliminates the need for the REQUESTING state.

Device selection has live previews that reuse the current local
audio and video tracks for the sake of internet explorer. This
means when the local video was muted, device selection would
show a muted message. It is preferred to show a live preview
even when muted.

The changes include:
- Passing device ids into DeviceSelectionDialog, not tracks.
- Setting default selected devices to use for live previews.
- Removing all checks in DeviceSelectionDialog involving local tracks.
- Catching and displaying errors when creating a live video preview.

Move the HD label into the newly renamed VideoStatusLabel
component. That way it cannot be possible for the audio only
label and the HD label to display simultaneously.

Audio only mode can be used to save bandwidth. In this mode local video is muted
and last N is set to 0, thus disabling all remote video.

When this mode is enabled avatars are shown.

In the filmstrip inlay, the avatar container holds the avatar
image. The image is set to 100% height, so it displays entirely
in the container. However, this does not adjust the horizontal
space created by the image in firefox, leaving whitespace to the
right of the avatar. The fix is to set the container height to
100% so that all its content will fit inside, automatically
adjusting the space created by the image width.

Create a new React Component for displaying a list of dial-in
numbers. The Component will fetch the numbers from a new
numberRetreviewUrl key/value set in config. If not present in
config, the Component will not be displayed.

AtlasKit DropdownMenu cannot be disabled, unlike Single Select.
The result is the isDisabled prop was not being honored. The
workaround is returning only the trigger element for the dropdown
and styling it to look like the dropdown is disabled. The text
for disabled device selection was changed along the way to fit
into the trigger.

Safari will prevent proper input behavior when user-select none
is applied. It prevents such actions as putting in a room lock
password or setting a room lock password. Other browsers allow
selecting on inputs while user-select is none.

AtlasKit Dropdown was recently updated to support fitting the
width of its container. However, AtlasKit Button, the trigger
element currently used for the dropdowns, does not fit the width
of AtlasKit Dropdown and stll has text overflowing out of its
button when there is an iconBefore prop passed in. Instead of
using AtlasKit Button, use a div and mimic the button look. This
allows the "button" to fit the container width and can display
ellipsized text within itself.

@virtuacoplenny, the changes of this commit are not necessarily in
source code that you introduced in
https://github.com/jitsi/jitsi-meet/pull/1499 but I saw violations in
files modified in the PR which I had to read in order to understand the
PR.

Converting the invite modal includes the following:
- Creating new react components to display InviteDialog. The
  main parent components are ShareLink and PasswordOverview,
  the later handles displaying lock state and password editing.
  These components do not make use of atlaskit as the component
  for input does not yet support readonly, so for consistency
  within the modal content no atlaskit was used.
- Using redux for keeping and accessing lock state instead of
  RoomLocker.
- Publicly exposing the redux action lockStateChanged for direct
  calling on lock events experienced on the web client.
- Removing Invite, InviteDialogView, and RoomLocker and references
  to them.
- Handling errors that occur when setting a password to preserve
  existing web funtionality.

On certain modal dimensions, the black background of the video
preview could peek through, making it look like the video has a
black line. The change is to remove the black background from
showing by default and having it only display when the video is
muted. Also, the video preview dimension stylings have been
changed to facilitiate smoother size adjusting with modal size
changes.

Instead of using AtlasKit Single-Select, use Dropdown. Dropdown
differs in that an icon can be specified for the trigger element,
whereas Single-Select currently supports icons for all elements,
and Dropdown can show all options incuding the already-selected
option.

This change does introduce the issue of the trigger element not
taking up 100% width of the parent. Supporting such would involve
overriding AtlasKit CSS. The compromise made here was to do a
generic override of max-width so the trigger elements at least
stay within the parent and aligning the trigger elements to the
right.

Some atlaskit components, such as field-text, inherit text color.
This is a problem with components that are white as they will
inherit $defaultColor, which is a light gray. So instead, for
the atlaskit modal, set a color for all the form content so it
can be inherited instead.

Atlaskit at times will have localized styling for font-size and
sometimes will not. The button component will inherit its
font-size whereas selectors have localized font-size of 14px. For
consistency, the cancel/submit buttons on the atlaskit modals
will also have 14px. The atlaskit story book examples also use
buttons with 14px font-size.

Cleanup existing logic for displaying and updating device
selection settings in the settings menu. In its place
is a button to open the device selection modal.

The Device Selection modal consists of:
- DeviceSelection, an overly smart component responsible for
  triggering stream creation and cleanup.
- DeviceSelector for selector elements.
- VideoInputPreview for displaying a video preview.
- AudioInputPreview for displaying a volume meter.
- AudioOutputPreview for a test sound output link.

Store changes include is primarily storing the list of
available devices in redux. Other app state has been left
alone for future refactoring.

We seemed to be using the names "film strip" and "filmstrip" (and,
consequently, their source code-conscious forms such as film-strip,
FilmStrip, etc.) In order to comply with our coding style which requires
a consistent one name for a given abstraction, choose one name and
rename the uses of the other name.

Wikipedia has a definition of a "filmstrip", I couldn't find a "film
strip". I guess our abstraction can be seen as what's described there.
When I google "film strip", I get results about "filmstrip" at the top.
That's why I chose "filmstrip".

Certain uses of "film strip" such as interfaceConfig.filmStripOnly and
in the external API I left untouched in an attempt to preserve
compatibility.

I wasn't sure whether CSS was tangled in compatibility so I made a
choice and renamed there was well.

All z-indexes found in css files have been moved into css
variables. If the z-index is used only once, the variable
name will be the same as the selector it is used in. If
the z-index is used multiple times, then the plain name
of $zindex# was used. This allowed a more confident
moving down of the toolbar so that the new modal dialog,
with z-index 500, could display on top of it.

#1436

#1411

This reverts commit b09e86352f.