Add: exps - fore/background model and related histogram comps
Add: exp - OpenCV bg substractor (3 models).
Add: wrapper - opencv hog/latentSVM/cascade detector.
Add: wrapper - frame tracker based on 2D features matching.
Mod: add debug details for feature2d tracker (tested).
Mod: add single channel histogram as building block.
Mod: implement CBWH for mean-shift init.