Use a single [userId, roomId] property for the chat page.
This gets read of the intermediate state where the userId property has
been updated but the roomId one not yet, which led to the page unloading
and reloading itself until both were properly set.
Side-effect: when starting Mirage after this commit for the first time,
the last saved page will not load and user must click a room or
other page manually.
If the room pane is below the default width (by user resizing or because
of narrow window), go to the room settings or a member profile will
automatically expand it as needed.
The pane goes back to its previous size once the settings/profile is
left.
If the window is narrow enough that expanding the pane normally would
reduce the timeline's width past its minimum, the pane is shown as an
overlay instead.
Allow opening context menu for AccountDelegate, RoomDelegate and
MemberDelegate by selecting an item with up/down (when focusing filter
field) and pressing the menu key.
