Programatic Close Release

A close() method is now publicly available, in case there is a (rare?) need for closing programatically. A corresponding completion block is also available, and it is separate from standard (interactive) close completion block.

A nifty little improvement was made in the completion phase, there is now virtually no delay between the time T when animations visually stop and the time T+n when the gallery actually disappears from view hierarchy and the underlying controller canvas is available for touches.