* feat(avatars): use initial service for getting images

* squash: capitalize and minor refactor of string concat

* ref(avatars): remove Avatar.js

- Rely on redux getting updated with new participant state
and any calls to getAvatarURL passing in the redux
participant state. This way the state within Avatar.js can
be removed.
- Clean up methods on UI.js. Because all state is in the
store, separate methods for updating the avatar aren't as
necessary. Instead centralize accessing of the avatar for
components outside of redux and centralize the call to
update avatars for non-react components.
- Controversial: cache a participant's avatarURL on the
participant state. Currently the participant's avatarURL
that is generated without jwt (which sets the avatarURL directly)
is not cached. Without cache, there can be many redundant
calls to APP.API.notifyAvatarChanged.

* Leverage middleware timing to diff avatars

One alternative implementation is to leverage middleware's
ability to intercept updates before and after redux has
upated and then compare avatarURLs.

* kill UI.getAvatarUrl

* profile button sets its own avatar url (solves update timing)

* remove calls to updating avatar outside of middleware

* update UI.js doc

* remove left over logic from initial implementation

* try to move local user fallback into selector func

* default to id 'local' in selector

The video will switch to the avatar and be tinted with gray. On the large view,
a text message indicating the user has connectivity issues will be shown.

Everything strophe related is now handled in lib-jitsi-meet project.

- Remove references to the model ContactList.
- Replace ContactListView with an empty element for attaching
  the React Component ContactListPanel, which has the same
  features as the old ContactListView.
- Create new selector for getting non-fake participants for
  ContactListPanel's props.
- Create a ParticipantCounter component to place in the contact
  list button. Previously ContactListView updated that but now
  it's a react component hooked into the participant state.
- Remove pub/sub that was used only by ContactListView.

- Re-use the native redux pinning implementation for web
- Remove pinning logic from conference.js
- To the native pinning add a check for sharedVideo so
  youtube videos do not send a pin event
- Add shared videos as a participant to enable pinning and
  so they can eventually get added to the filmstrip
- Emit UIEvents.PINNED_ENDPOINT from middleware

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.