Fixes #866
Removing the erroneous if statement around drawing a control's background allows there to be
borders only on some sides of a skinned control.
Using NEAREST filter instead of LINEAR on theme textures to fix blurry borders.
Fixes a typo in ImageControl's UV calculations.
Allows opacity to affect ImageControls.
Merge branch 'next' of https://github.com/blackberry/GamePlay into bugfix
Merge pull request #911 from ablake/next

More small UI bug fixes.