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.
The only behaviour that should have changed here is that
presence is also set to online when switching back to the
tab/window.
Presence is not set to unavailable when coming back to the window/tab,
as that might be a bit invasive, but only when timing out.
Before, UserActivitity emitting actions meant that the user had very recently interaction with their hardware.
Now it means they are likely looking at the app.
You can attach a timer that is aborted when we think the user
stops looking at the page
(or hasn't touched their hardware for 2 minutes).
This works better than the previous approach for larger timeouts,
like the 30s we're about to implement for out-of-view RMs
make mx_fadable not do anything anymore, and make room settings
full size.
Room settings haven't been designed yet, so all of this will
have a full pass when we have a go at it.
up till now, resize received the offset of the resize handle
within the container upon resizing, and would then calculate
it's new size. For this first item in the container, this is
the same, and has therefor not been a problem yet.
Now however, we'll need to be able to programatically
(from localStorage) set the size of any roomsublist,
so need a method we can call with just the size and not an offset
within the container. The resizer calls the new method,
which subsequently calls resize.
This also has the nice side-effect that you can now easily
call super.resize after having transformed the new item size
