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. 

This reverts commit 618fbf55.

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).

Two colormaps removed from the list of colormaps, as they are no visually improved enhancement to a Jet colormap.

Exceptions now go into CV_Error. Added thresholding to the FaceRecognizer and updated the demo accordingly.

Several exceptions added to the available FaceRecognizer classes and helper methods, so wrong input data is reported to the user. facerec_demo.cpp updated to latest cv::Algorithm changes and commented.

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