Update libGDX pom's.

Update libGDX version from 0.9.9-SNAPSHOT to 1.0-SNAPSHOT in
nifty-examples-libgdx and nifty-renderer-libgdx pom's. Add helpful
comments to the desktop and android pom's in nifty-examples-libgdx.
Clean up formatting of nifty-examples-libgdx and nifty-renderer-libgdx
pom's.
Merge pull request #161 from 3xp0n3nt/update-libgdx-poms

Update libGDX pom's.
bring back getElements() as a @deprecated method

was removed by fd893333605edc353828cf1dd60584afae3a1b20 but really
should be marked @deprecated for easy migration to 1.4 from 1.3
Publish ButtonReleaseEvent's for buttons.

This allows subscriptions to ButtonReleaseEvent's using
NiftyEventSubscriber annotations, rather than having to use the "old"
method of interactOnRelease.
Merge pull request #162 from 3xp0n3nt/button-release-event

Publish ButtonReleaseEvent's for buttons.