Added OpenNI 2 grabber.

OpenNI 2 grabber based on ROS implementation by Julius Kammerl. CMake check prevents building OpenNI 1.x and 2.x grabbers simultaneously.
Added script to copy OpenNI 2 redist folder to bin.

Added command to copy the contents of the OpenNI 2 redist folder to the bin directory. This follows the new OpenNI 2 deployment model, where each application has a private copy of the binaries.
Added OpenNI 2 viewer app to visualization module.
Changed default viewpoint for OpenNI 2 viewer app.

Needed to look down +Z axis to see point cloud.
Fixed abstraction around exiting OpenNI 1.x grabber.

This should help with switching between OpenNI 1.x and 2.x grabbers.
Added OpenNI 2 check when building kinfu.
Added OpenNI2 library checks when building kinfu app.
Added OpenNI 1.x/2.x switches.
Masked oni_grabber errors when the OpenNI 1.x wrapper is not used.
Added conditional compile instead of changing OniGrabber cast type.

Should prevent regression problems when using OpenNI 1.x.