Prototype of image registration support for Kinect driver.

Hi OpenNI folks,

I created a prototype of depth-to-color image registration for Kinect driver as well as a few code readability improvement. I hope this prototype could be helpful for the early support of this feature.

I had some applications that needed this feature, but I came to know OpenNI2 did not support it yet from the community forum (http://community.openni.org/openni/topics/how_can_i_align_with_kinect). I thought I could contribute by creating a prototype since I already achieved Kinect SDK - OpenNI 1 mapping including this feature in my previous work (http://code.google.com/p/kinect-mssdk-openni-bridge/). I just applied the same idea in this prototype.

I wrote this code based on my best guess about the necessary background including the design philosophy, the intended spec, the coding convention, etc., so it might be wrong or inconsistent. Please feel free to review and fix it. If you want me to fix it, I would be happy to do my best.

Thank you very much,
Tomoto