New OpenNI2 driver

Added an OpenNI2 driver to hwdrivers. It permits to access several OpenNI2 sensors simultaneously. Two examples are included.

rawlog-grabber can record data using this driver. Some .ini files are provided for that.

Some minor changes in PbMap are also included.

** It looks like the permission of some files have been modified, I'm not sure about how to handle this in this pull request.