Changed css to display overflow chatroom dropdown bottom/left
Added focus() function to ChatRoomViewController
Changed ChatRoomViewControllerManager's focusOnChatRoom to call the
focus function on the ChatRoomViewController

ACE-63
Removed reference to ChatRoomViewControllerManager from
ChatRoomViewController. 
Removed code that checked if a ChatRoomViewController is in the hidden
overflow list from ChatRoomViewController and created a contains()
function in HiddenChatRoomViewController to handle that responsibility.
Added call the new contains function from ChatRoomService in order to
set focus on the hidden chat room prior to displaying chat message.