Updated the lambda coefficient to the one suggested in the original paper (http://www.robots.ox.ac.uk/~joao/publications/henriques_tpami2015.pdf, page 11, Table 2) which works (for me) better then the previous default one.

Use ROI selector in python samples

* Fix kcfTracker when called from Python bindings. The variable boundingBox in updateImpl when called from Python is initialized with 0s and it needs to be updated with the tracker state.

* Fix to return the bbox correctly in the first frame in Python

Required for MSVC builds - shouldn't affect result otherwise.

Removing all shadowing variables, make functions to const, make the table of color-names become static

Fixed: ROI extraction when the given ROI is out of image; made the max_patch_size to be adjustable; add the CN feature extraction method

+ add KCF Tracker, initial commit, added: tutorial, trackerKCF.cpp, modified: tracker.cpp, tracker.hpp