Gallery2: add some video features

including: previous/next video play mode, screen mode,
fast forward/rewind button, step settings.

Change-Id: I3f4890c4dd95956e0eca889a5fd8b8d83b8d542e
Gallery2: Customize features for regional package

- Support user link to net to see more images.

Change-Id: I4c095bd124057c996d4bf0d3a4a035b6587db640