* feat(feedback): convert to react and redux

- For styles, remove "aui-dialog2" nesting so existing styles
  can be reused.
- Remove Feedback.js and replace with calls to redux for state
  storing and accessing.
- Add dispatching to FeedbackButton instead of relying on jquery
  clicking handling so the button can be hooked into redux.

* address feedback

* remove calling to not show feedback for recorder and filmstrip

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.