This started off as me just wanting to adjust the margin of the search bar but grew a touch ...
- Cleanup margins especially make the member search bar have the same padding as everything else
- Move room information title to header and align all buttons right.
- Make the room name actually bold
- Remove highlight from the user list item after the menu is closed
- Always use actual width so that the drawer isn't wider when modal
- Use control instead of pane for the search bar as the padding works more consistently
- Use BasicListItem instead of AbstractListItem for the member list as this has the layout predefined

While this option works, it doesn't make much sense since there isn't
much of a good reason to talk to oneself aside from for testing
purposes. The created conversation also has confusing UI, showing as an
"empty room", not a DM. If needed, creating an empty room with E2E
encryption has the same effect as creating a private chat with
yourself.
Closes#446.
Previously, when there was no avatar set, the source property of Avatar was still set to 'image://mxc/',
which caused Avatar to load that from the imageprovider. The imageprovider can't provide an empty image and aborts with error