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

fixed 2 build problems on MacOSX (highgui with ffmpeg, opencv_world); added macro CV_INIT_ALGORITHM for simpler algorithm registration (ticket #1876)

Added new performance tests for calcOpticalFlowPyrLK and buildOpticalFlowPyramid; extracted private header from lkpyramid.cpp

Android samples are updated: onPause()/onResume() release/open camera, a message is shown on camera open error, minor fixes in code and resources

Shortened CMake script for opencv_world. Fixed opencv_world link with non-Visual Studio generators on Windows.