Up until now we relied on implicit loading of middlewares and reducers, through
having imports in each feature's index.js.

This leads to many complex import cycles which result in (sometimes) hard to fix
bugs in addition to (often) breaking mobile because a web-only feature gets
imported on mobile too, thanks to the implicit loading.

This PR changes that to make the process explicit. Both middlewares and reducers
are imported in a single place, the app entrypoint. They have been divided into
3 categories: any, web and native, which represent each of the platforms
  respectively.

Ideally no feature should have an index.js exporting actions, action types and
components, but that's a larger ordeal, so this is just the first step in
getting there. In order to both set example and avoid large cycles the app
feature has been refactored to not have an idex.js itself.

* Button conditionally shown based on if the feature is enabled and available
* Hooks for launching the invite UI (delegates to the native layer)
* Hooks for using the search and dial out checks from the native layer (calls back into JS)
* Hooks for handling sending invites and passing any failures back to the native layer
* Android and iOS handling for those hooks

Author: Ryan Peck <rpeck@atlassian.com>
Author: Eric Brynsvold <ebrynsvold@atlassian.com>

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.

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.

Move logic to open device selection outside of SettingsMenu so
it can be called independently by either SettingsMenu or by
the settings button itself if no other settings but devices will
be displayed.

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.

When callstats is not configured hide the button.

As an intermediate step on the path to merging jitsi-meet and
jitsi-meet-react, import the whole source code of jitsi-meet-react as it
stands at
2f23d98424
i.e. the lastest master at the time of this import. No modifications are
applied to the imported source code in order to preserve a complete
snapshot of it in the repository of jitsi-meet and, thus, facilitate
comparison later on. Consequently, the source code of jitsi-meet and/or
jitsi-meet-react may not work. For example, jitsi-meet's jshint may be
unable to parse jitsi-meet-react's source code.