Add the ability to search in the user directory for friends.
This adds an option in roomlist when on the friends tab and opens a search dialog when clicked. The new search model searches the user directory for the given filter term.
Update the UX to refer to structure direct chats as friends. The direct chats are pulled into their own tab in the space drawer.
The `UserDetailDialog` is also updated to check whether a direct chat already exists and if not ask to invite as friend.
Add a space homepage with the ability to both create new room and add existing rooms to the space. This uses a tree model for the space hierarchy and will go to any number of levels. The user should only see the add options if they have appropriate permissions.
This MR also combines the create space and room pages and adds a lot of optional functionality for managing space children.
Previously, some functions that conceptually belong to the connection needed to be in the Controller, since we didn't have a place to put them.
This fixes that by extending the Connection class in a similar way as we extend the Room class.
