* Add tracking-by_matching code and sample
* Make interface for PedestrianTracker
* Replace PedestrianTracker -> TrackerByMatching
* Make proper filtering by class id in tracking_by_matching
Also make the sample build in the case when opencv_dnn module is not
built.
Also help is added.
* Remove TODO-s from tracking_by_matching code
* Add parameter frame_step, add copyrights, fix warnings
* Remove copyright from tracking_by_matching
* Rename check macros and remove obsolete mentions of pedestrians
* Tune default thresholds in tracking_by_matching sample
* Add description of classes and factories
* Remove unrequired EOL-s at the end of files
* Replace pointers by references for output parameters
* Fix some warnings found by buildbot
* Fix warning from buildbot, tune some thresholds in tracking_by_matching
* Replace pragma once by ifndef-define clause
* Fix more Windows warnings
* Change case of methods of TrackerByMatching class
* Change name of methods to CamelCase in TrackerByMatching
* Make more convenient check macros in tracking_by_matching.cpp
* Simplify tracking_by_matching sample
* Fix Mac error in tracking_by_matching
