Fix crash caused by using uninitialized m_replayInputLog in JSGlobalObject.
Make the backend actually load/unload recordings when capturing. Keep
a map of created recordings in the backend ReplayAgent.

Closes #235.
Frontend: extract the list of recordings into RecordingsModel.
Significant work on the recordings panel. Shows multiple recordings
and their creation times, and switches between tables of recording
inputs.

Closes #82.
Closes #226.
Closes #227.
Frontend: Insert a temporary tree item into Recordings panel when capturing a recording.

Closes #245.