Adding mac+mac screensaver+ipad support

The main view has been rewritten to use a drawrect call instead of multiple subviews, this xxiivvBifView compiles as a UIView or NSView subclass depending on the target architecture.

The BifView will also automatically create bigger versions of the grid tiles for larger screens using the nearest neighbor algorithm. 

All images have been changed to lossless pngs instead of jpg.

The readme contains a list of todo items before this should be released.