This allows for filtering of the RoomList by group. When a group is selected, the room list will show:
- Rooms in the group
- Direct messages with members in the group
A button at the bottom of the TagPanel allows for creating new groups, which will appear in the panel following creation.
In order to provide feedback when adding a room to a group, the group summarry store needs to be extended to store the list of rooms in a group. This commit is the first step required.
The next step is to get the GroupRoomList listening to updates from GroupStore and expose the list of rooms from GroupStore.
(We're running out of words to describe the hierachy of things that store things)
