Merged lda fix from 2.4 branch (Fixed reconstruction, so that the mean is correctly added to the reconstructed image.)

Added a check of the DetectionBasedTracker's inner state in the main thread function of this class. 
This change should fix a multithread bug in the class.

FaceRecognizer class is now derived from Algorithm, therefore it's possible to set and retrieve the parameters using conventional Algorithm::set and Algorithm::get methods

lot's of changes; nonfree & photo modules added; SIFT & SURF -> nonfree module; Inpainting -> photo; refactored features2d (ORB is still failing tests), optimized brute-force matcher and made it non-template.

minor build system changes (now cuda code in opencv_core is compiled using CUDA_ARCH* cmake variables)

 [~] Automatically tracked dependencies between modules
 [+] Support for optional module dependencies
 [+] Options to choose modules to build
 [~] Removed hardcoded modules lists from OpenCVConfig.cmake, opencv.pc and OpenCV.mk
 [+] Added COMPONENTS support for FIND_PACKAGE(OpenCV)
 [~] haartraining and traincascade are moved outside of modules folder since they aren't the modules