First CMake integration of OpenNI2
OpenNI2: Better automatic detection from CMake
DifOdo integration with MRPT + 2 examples OpenNI2

DifOdo (differential odometry) class is added (CDifodo)
2 applications are included to use it:
- "Difodometry-datasets" to test its performance with the datasets from
Freiburg/TUM.
- "Difodometry-camera" to perform visual odometry in real time with an
RGB-D camera.

Independently, 2 examples are added to illustrate how to manage a RGB-D
camera with the OpenNI2 middleware.
Bug fixed: generic address of rawlog

Each user has to specify the address of the rawlog when using the
"Difodometry-Datasets" app.
- Fixed encoding of some files to UTF8
- Updated copyright notices.
Bugs fixed in "DifOdometry" apps
Change in measuring Difodo execution time

It now includes the time spent in "filterSpeedAndPoseUpdate()" (as it
should)
Bug fixed: reading the ground truth

The first ground truth data wasn't read properly
Formalities with MRPT
Fixed build errors in GCC/Linux.
Small corrections in DifOdo Apps

Moreover: Spanish sentence translated to English in ReactiveNav3D app...
Useless code lines deleted in DifOdo_Camera app
More "code cleaning" in Difodo class and apps
Merge remote-tracking branch 'origin/integrate-openni2'

Conflicts:
	doc/doxygen-pages/changeLog_doc.h