Author: James Pratt
MDL-41759 quiz statistics : break down responses for each variant
http://git.moodle.org/gw?p=moodle.git;a=commit;h=4922e79f3e20d4909abf9bffa513676d807a9f5f
http://github.com/moodle/moodle/commit/4922e79f3e20d4909abf9bffa513676d807a9f5f
+ 2.7 en [detailedanalysisforvariant,quiz_statistics]
+ 2.7 en [variant,quiz_statistics]
+ 2.7 en [variantno,quiz_statistics]