Also move cv::linemod to own header

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

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

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

class LevMarqSparse is not tagged CV_EXPORTS, 
so the contrib module,  built the on win using vs won't contain that symbol,
trying to create an instance of LevMarqSparse will lead to a 'undefined symbol' err, because it did not make it into the library. 

Invalid links and refences fixed.
SpaeseMat class documentation updated.

This reverts commit 618fbf55.

This reverts commit 94b97b7a.

This reverts commit 9b8c4739.

This reverts commit 618fbf55.

added openfabmap code, contributed by Arren Glover. fixed several warnings in the new versions of retina filters

Issue #2231: Attempt to fix segfault, when copying labels. LDA needed to be updated to generate the Wrapper correctly.

FaceRecognizer supports updating a model now. Documentation has been updated to reflect latest changes.

Updated the train method to be an InputArrayOfArrays, so the Python wrapper now generates the correct code (and it works).

Changed DetectionBasedTracker a bit to make its method addObject to return an integer value -- the id of the new added object.