Update all viewports by default.

Please don't seem to get that resize is an important event.
Adjust UVs to avoid seams.

@MobiDevelop, @badlogic and others, what do you think? It moves the UVs of all tiles half a texel inward. This was the only way I found to get rid of seams. Using texture packer with duplicate padding works, but I still had a problem when packing four 512x512 images into a single 1024x1024 image, since there is no room for packing. This fix seems to get rid of all seams, maybe even when not using duplicate padding.

I wanted to adjust the AtlasRegions in AtlasTmxMapLoader but TextureRegion doesn't allow the UVs to change without affecting the region width and height, which seems a little jacked. Had to settle for doing it at render time.
Merge branch 'origin/master'