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.
Pull the generic aspects from Room search and join room pages into it's own component. This is done in anticipation of using the new generic search page for a user search functionality.
- `SearchPage` is now used for the generic version with the old one being renamed `RoomSearchPage`
- `JoinRoomPage` is renamed to `ExploreRoomsPage` inline with everywhere else in NeoChat
There is also some cleanup of the code for both search pages in here.
