Does not fix the read status yet, for that we need to compare read
receipts for all events after the last visible event.

The UI still looks ugly, but I have no good idea atm.

fixes #134

Don't send inbound session to self and claim and send all keys at once.

Also fixes a bug with an empty room settings window introduced in the
port.

Also fixes some resize issues with stupid workarounds to our resize
logic. This really needs to be cleaned up at some point!

This is necessary to support having a picker within QML.
Eventually, this should replace the existing widget-based one.

This turns `paginationInProgress` field of `TimelineModel` into a `Q_PROPERTY`, so the Ui can bind to it.
For the moment, I'm showing the same spinner as we do during initial sync. It's not ideal, on the count of being giant and in the middle but it's better than nothing. We can make it more subtle later.