Also, removed the one from modules/python/src2/cv.py and cleared its
executable bit, since it's not a script.

e.g. <opencv2/core/core.hpp> become <opencv2/core.hpp>

Also renamed <opencv2/core/opengl_interop.hpp> to <opencv2/core/opengl.hpp>

Added a simple CMakeLists.txt to the facerec_samples, which are not included in the samples folder. Makes building these samples a lot easier.

Fixed facerec_eigenfaces.cpp demo sample: it contained hardcoded values, which made wrong element access possible. Fixed unsigned integer/signed integer warnings in facerec.cpp.