Added FINDOPENNI.cmake and FindNITE2.cmake

The two new files were directly added to /cmake dir so the modified
Cmakelists.txt finds it and the route to the libraries and headers is
linked to the project.

- added cmake files solve the problem only on Win
- usage of the headers e.g.: #include <OpenNI.h>
- IMPORTANT! CMAKE_INCLUDE_PATH and CMAKE_LIBRARY_PATH must be modified in
  order to find the header and library files (\Include and \Lib
  directories where NiTE2 and OpenNI2 is installed)