* feat(quality-slider): initial implementation

- Add new menu button with an Inline Dialog slider for
  selecting received video quality.
- Place P2P status in redux store for the Inline Dialog
  to display a warning about not respecting video quality
  selection.
- Respond to data channel open events by setting receive
  video quality. This is for lonely call cases where a
  setting is set before the data channel is open.
- Remove dropdown menu from video status label and clean
  up related js and css.

* first pass at addressing feedback

- Move VideoStatusLabel to video-quality directory.
- Rename VideoStatusLabel to VideoQualityLabel.
- Open VideoQualitydialog from VideoQualityLabel.
- New CSS for making VideoQualityLabel display properly.
- Do not render VideoQualityLabel in filmstrip only instead of hiding with css.
- Remove tooltip from VideoQualityLabel.
- Show LD, SD, HD labels in VideoQualityLabel.
- Remove action SET_LARGE_VIDEO_HD_STATUS from conference.
- Create new action UPDATE_KNOWN_LARGE_VIDEO_RESOLUTION in large-video.
- Move VideoQualityButton into video-quality directory.
- General renaming (medium -> standard, menu -> dialog).
- Render P2P message between title and slider.
- Add padding to slider for displacement caused by P2P message's new placement.
- Fix display issue with VideoQualityButton displaying out of line in the
  primary toolbar.

* second pass at addressing feedback

- Fix p2p inline message color
- Force labels to break on words
- Resolve rebase issues, including only dispatching quality
  update on change. Before there was double calling of dispatch
  produced by an IE11 workaround. This breaks now when setting
  audio only mode to true twice.
- Rename some instances of quality to definition

* rename to data channel opened

* do not show p2p in audio only

* stop toggle audio only icon automatically

* remove fixme about toolbar button

* find closest resolution for label

* toggle dialog on button click

* redo last commit for both button and label

* Fixes some toolbox/toolbar styles and variables

* [squash] Fixes variable name to fit better its purpose

* [squash] Fixes secondary toolbar variable name

* fix(filmstrip-only): vertically align center the toolbar

Use top 50% to position the toolbar's top at the vertical center
of the iframe. Then use transform 50% to move the toolbar itself
up 50% so its middle matches the middle of the iframe.

* squash: toolbox should center with filmstrip

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.

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