fixes #2

fixes #107

fixes #128

Automatically dismiss unread notifications when the window regains
focus.

fixes #111
fixes #68

fixes #134

The color scheme of nheko obeys the default color theme of Qt
(i.e. the system theme). It uses a Qt stylesheet to accomplish this,
which means replacing the color theme with a custom theme would only
be a matter of writing a new style sheet and loading it into the app.

- Fixes high cpu issues caused by the serialization of the whole
  in-memory state.
- Display name changes are now visible in the timeline.

* Initial "join room" feature.
* React correctly to remotely joined rooms.
* Leaving rooms implemented both locally using the room menu
   in nheko, and reacting properly when leaving a room remotely 
   from another client.

closes #11

- Rooms without any history will be shown.
- Room's state will be kept in sync and any updates will be visible.

- Add border width on Badge

Logout from the current session and invalidate the current token