modules/objectdetect/src/detection_based_tracker.cpp: made unique_lock<mutex> local to each function
samples/cpp/dbt_face_detection.cpp: fixed warnings on loop in Visual Studio

* bypass makro

* syntax

when true, use signed gradient for the angular histogram computation.
default to false for backward compatibility.

removed ERFilter (to be moved to opencv_contrib/modules/text) and lineMOD (to be moved to opencv_contrib/modules/rgbd)

put the detection-based tracker back (to objdetect module), so that the Android face detection sample builds fine. The patch by Konstantin Matskevich that adds C++11 threads support has been merged in too. Also, fixed compile error in the doc builder.

removed contrib, legacy and softcsscade modules; removed latentsvm and datamatrix detector from objdetect. removed haartraining and sft apps.
some of the stuff will be moved to opencv_contrib module.
in order to make this PR pass buildbot, please, comment off opencv_legacy, opencv_contrib and opencv_softcascade test runs.

fixing issues from coverity scan 1167937, 1167938, 1167939, 1127248 (http://scan.coverity.com/projects/169?tab=Overview)