Change the LastActivity sort order to Activity and update to a more flexible way of sorting based on an order from model roles. Add options to actually switch between Alphabetical and Activity Based on some old work by @tdfischer implements #103
Make sure that the room isn't already in the model before appending. Move it if it's in the wrong catgeory
This makes sure that the room disappears from the tree view
Use a tree model for the room list closes network/neochat#156 BUG: 456643
