* fix(participant-pane) Use the sorted participant list from redux instead of sorting it on every render making it better performant. Match the participant order with that of the order in the filmstrip. Also move the participants with raised hand to the top of the list.

* ref(filmstrip) Move enableThumbnailReordering flag to testing section.

* fix(participants) Add new selectors for getting sorted participants.

enableThumbnailReordering flag (enabled by default) will be used to check if the thumbnails needs to be reodred in the UI.

* feat(Filmstrip): Reorder the visible participants in the filmstrip.
The participants are ordered alphabetically and the endpoints with screenshares, shared-videos and dominant speakers (in that order) are bumped to the top of the list. The local participant is also moved to the top left corner as opposed to the bottom right corner.

* squash: Implement review comments.

* squash: store alphabetically sorted list in redux and move shared videos to top.

* squash: Use the DEFAULT_REMOTE_DISPLAY_NAME from interfaceConfig for users without a display name.

Due to how the filmstrip size if computed I don't think there is a good way to
animate the change in size, so just ignore the toolbar, it will be hidden soon
enough.

- Lower the inter-tile margin to 2px
- Remove the 100px top/bottom margin when the toolbar is hidden

Moves the logic from all different places into single state
listener to combine all inputs into a single output.

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.

* ref(Filmstrip): Optimize resizes.

* fix(thumbnails): resize.

* fix(thumbnails): Issue with height 0, width 0.

* doc(Filmstrip): Improve JSDoc.