* factor out the call to MatrixClient.search to a separate _getSearchBatch (so
that we can reuse it for paginated results in a bit)
* Don't group cross-room searches by room - just display them in timeline
order.
Call /forget when the forget button is clicked. Number of shortcomings:
- We need to lazy load the historical list (atm we never get the list of left
rooms; things only go into that list if you leave the room whilst running)
- Once a room is forgotten we need to physically nuke it from the JS SDK.
- Need icon for forget room.
