Apriltag (#1570)

* doCornerRefinement to CornerRefinementMethod :: detected contours points are used to detect the corners

* some little corrections

* samples edited

* documented :)

* tabs corrected

* Docu corrections

* refinement for all candidates

* refinement for all candidates :: copy paste error corrected

* comment

* apriltag

* whitespace corrected

* corr ini

* correction :: warnings, c4244, preprocDirect, ...

* try to ignore 4244, fix 2131, add test, and ...

* try to ignore 4244

* test duplicate deleted

* corrected test, warnings

* test :: correction

* warnings

* warnings and test

* warnings

* perspective test, warning corrections

* warning a_q_t

* warning

* warning

* 3 clause BSD license

* stacksz and typo

* eliminate build warnings

- cv::fastAtan2()
- cvFloor()

* small code refactoring

* fix isfinite()

* get rid of manual calloc/free calls

* update file headers