Add a pocket display

We need to display the pocket. The existing advertisement view should be able to be re-used to provide much of this functionality. Pocket operations needed:

Like pocketed ad. Remove ad from pocket. Access individual ad from pocket by tapping the ad (should poke the endpoint /user/pocket_entries/{id}, so we can log the analytics for the access of the pocket entry.)

Clearly addition of the ad to the pocket should be accessible from the main activity.