some updates

• added an explicit quit button the playtest screen (instead of relying on android back button which many people don't know how to trigger)
• automatically crop new images down to remove excess empty pixels
• added a background grid to help you see that you're moving the camera instead of an object
• added a fade out/in for the pinned objects so they only show when you're close to 1:1 scale
• put the add old add photo button back

trello: trello.com/b/jZoV37N7/...