Improved the GCD dispatching in TileOverlayRenderer's drawMapRect function.
Crashes less and seems to work faster.  Also improves the spinning wheel such that it runs once during heavy processing rather than starting and stopping every couple milliseconds.

Also added an Orientation Notification so that all UI Items except for the Map and the Opacity Slider are hidden in landscape mode.  This gives the user more screen space to view the map when desired.
Refined TileMapViewController's design.
Headline label now shows whichever tile who's center is closest to the screens center.

(Weird thing noticed:  Tiles 5 and 6 seem to share the same center?  That doesn't seem right)
Empty Cache Button Added  (functionality not implemented yet)
Merge remote-tracking branch 'origin/master'