Create FriendRequest class

- Move Facebook login queries into AppDelegate
- Present LoginViewController if user is not logged in
- Re-implement finding friends; controller is no longer subclass of
FBFriendPickerViewController
- Create FriendRequest class in Parse; categorize friend type
Add friends and load locations

- Send and cancel friend requests
- Accept friend requests and check for accepted friend requests
- Load friend location and view on clock
Enable Core Data

- Add timestamps to locations
- Use Core Data to enable geofence persistence
Merge branch 'get-locations' into develop