Change the `JoinRoomPage` so that it emits a `roomSelected` signal with the selected delegate's info instead of calling the functions to join or enter the room itself. This is so that the `JoinRoomPage` can be used for other purposes like selecting an existing child to add to a space.
Also modernize the codebase where possible (e.g use required properties,
reorder properties, fix warnings, don't use Action when not needed)
Signed-off-by: Carl Schwan <carl@carlschwan.eu>
