added two new eye detection cascades and updated license in haarcascade_mcs_*.xml files

We have rewritten the haarcascade_mcs_*.xml file headers to avoid any further misunderstandings, plus including two more recent xml files for left and eye detection that are able to be faster with enough accuracy in some scenarios (haarcascade_mcs_lefteye_alt.xml and haarcascade_mcs_righteye_alt).