the idea is that it will keep a RoomViewStore for every
room on the screen, and also keep track of which one is
the current one.
For now, it just replicates the existing functionality of
having just 1 room on the screen.
Since the RoomViewStore just has access to a local dispatcher
and not the global anymore, all dispatching of actions
needs to be moved to the OpenRoomsStore, so room alias resolving,
event forwarding, ... is moved there.
