OpenNI2 Driver fixes and improvements

Hi,
in these four commits, various fixes and improvements have been made:

- Fix a typo that resulted in an error in z coordinates
- Exit cleanly when playback (with no looping) has finished
- Add video file information when playback with no looping has finished
- During startup of the driver, additional info about OpenNI/NiTE version, video resolution and fps info is printed
- Minor documentation fixes.

Commits rebased and squashed :)
Thanks!

Kostas