Added favorites button

Summary: Added favorites button to fragment_list_view to add a stop to the favorites. Now there's a little star near the serched bus stop name to add it to the favorites.

Reviewers: valerio.bozzolan

Reviewed By: valerio.bozzolan

Subscribers: Libre BusTO

Tags: Libre BusTO

Maniphest Tasks: T18

Differential Revision: https://gitpull.it/D17