Kinect2Grabber with example

This is a grabber for the kinect v2. Since libfreenect2 is still in development I created a preliminary version of the grabber with an example as app instead of inserting it in IO. The grabber produces 512x424 clouds, but I am planning to create clouds of dynamic dimensions. The support for it is already available in the code, but I have to make some fixes. The cloud is already registered, if the correct calibration is provided. There is the possibility to calibrate the kinectv2 using the grabber, by providing a set or depth/rgb images. I add also my own calibration files even if the grabber supports calibration.