Enable getting reject levels and level weights in cv.CascadeClassifier.detect

[ShakedDovrat]

OpenCV has an undocumented overloading of CascadeClassifier's detectMultiScale method, which
returns the reject level (cascade) and level weight of each of its detection.
For more information see:
http://codeyarns.com/2014/10/30/how-to-get-detection-score-from-opencv-cascade-classifier/
http://haoxiang.org/2013/11/opencv-detectmultiscale-output-detection-score/
This code enables calling this overloaded method, by requesting three output arguments from cv.CascadeClassifier.detect instead of one.

[amroamroamro]

@ShakedDovrat
FYI we already have all those variants exposed in the master branch (there are actually 3 variants in opencv 3.x, and only 2 variants in opencv 2.x).

Perhaps it would be better to backport the existing code from master to v2.4, see:

• https://github.com/kyamagu/mexopencv/blob/master/src/+cv/private/CascadeClassifier_.cpp#L222
• https://github.com/kyamagu/mexopencv/blob/master/+cv/CascadeClassifier.m#L229

For reference, here is the relevant commit when we updated CascadeClassifier to 3.x: 5a3f2c4 (mainly pay attention to the changes related to detectMultiScale).