Added a writeFormat() method to Algorithm which must be called by the
write() method of derived classes.

fixes #5443

fixes #5853 #4740

Document say probs will have CV_64F type. But in effect, it has CV_32F type.
http://docs.opencv.org/3.0.0/d1/dfb/classcv_1_1ml_1_1EM.html#a2ea7da92a75bc7a7d665c241f547b9b9

Fix a bug. When reading from a saved model, function decomposeCovs() will be called. And if covMatType is COV_MAT_DIAGONAL, covsEigenValues is computed using SVD and eigen values are sorted so that the order of eigen values is not preserved. This would lead to different result when calling function predict2. This issues is discussed here: http://stackoverflow.com/questions/23485982/got-different-empredict-results-after-emread-saved-model-in-opencv.

2. Algorithm::load/save added (moved from StatModel)
3. copyrights updated; added copyright/licensing info for ffmpeg
4. some warnings from Xcode 6.x are fixed

initial commit; ml has been refactored; it compiles and the tests run well; some other modules, apps and samples do not compile; to be fixed

Made all STL usages explicit to be able automatically find all usages of
particular class or function.

added dedicated <modname>_init.cpp files with initModule_<modname>() functions and all the relevant structures; made BackgroundSubtractorMOG/MOG2 derivatives from Algorithm; cleaned up MOG2 implementation and made it multi-threaded.