Author: Tim Hunt
MDL-42105 questions: let attempts have a max fraction > 1.
This parallels question_attempt->minfraction, which allows the
fractional mark to go below zere.
This is needed to allow the certainty-base marking behaviours to work
better.
http://git.moodle.org/gw?p=moodle.git;a=commit;h=4e3d829350867491c3cf6d8651a09d26904c7b85
http://github.com/moodle/moodle/commit/4e3d829350867491c3cf6d8651a09d26904c7b85
+ 2.6 en [technicalinfomaxfraction,core_question]