Camera: fix gfx undefined buffer issue

clear the render target before drawing, fix the undefined buffer
mess up issue of preview layer

Change-Id: I093fc0bdaf292fed2bc7f1a6d2678a94f25c9d55
CRs-fixed: 503216 506709
Gallery2: Fix detail dialog image count

This commit fixes the displayed image index which needs
to be count up by 1 to make sense for the user.

Before: http://goo.gl/BeRp8Z
After:  http://goo.gl/N3xvX6

Change-Id: Ib8d782188207d9ee7444316e8426b8215c67e594
Control zoom with volume keys in camera and camcorder

Change-Id: I3e7dc1811f6273a5918163d15d875b06064d1f57