Added function decomposeHomographyMat. New files added are homography_decomp.cpp and test_homography_decomp.cpp.
Modified files calib3d.hpp and camera_calibration_and_3d_reconstruction.rst.
Fixed warnings and parameter name mismatches, added #include needed in some platforms.
updated documentation for decomposeHomography
added comment.
Merge remote-tracking branch 'upstream/master' into HomographyDecomp
Merge pull request #2671 from syilma:HomographyDecomp