Updating styling for iOS 7

Removing gradients and rearranging UI to match Mike T's mockups.

I added a reference to the 4-inch launch image so that the
app can start up non-letterboxed on a 4-inch screen.

Mike T has updated the mobile skin repository with new image names,
requiring complementary updates to the application.
Merge branch 'master' into topic/update-style

Conflicts:
	OpenTreeMap/src/OTM/Controllers/OTMMapViewController.m