Can't do it for QtWidgets code. We need to fully transition, before we
can fully switch over probably.

 - hides the overlay when prompting for download location
 - cancel re-shows the dialog
 - success closes the overlay
 - would be nice to have a return code from the download fn in
 mtxclient.

Closes #140

Fixed bug caused by me forgetting what types im using (invites appearing at the bottom of the list instead of the top when priority sorting was off)

i was confused when a room with me and two friends showed as "user1" and
3 others.