Author: Henning Bostelmann
MDL-30031 Adaptive question behaviour: ignore invalid answers without penalty
http://git.moodle.org/gw?p=moodle.git;a=commit;h=fb93cfac00e36718b88340801fa28d86d2acf344
http://github.com/moodle/moodle/commit/fb93cfac00e36718b88340801fa28d86d2acf344
+ 2.2 en [disregardedwithoutpenalty,qbehaviour_adaptive]