Author: Jetha Chan
MDL-36009 grader_gradereport: filler and extra user cells should not be headers
http://git.moodle.org/gw?p=moodle.git;a=commit;h=3be4c8751c94514e8918b3fbc5c5a6b7bcca64ff
http://github.com/moodle/moodle/commit/3be4c8751c94514e8918b3fbc5c5a6b7bcca64ff
+ 2.7 en [summarygrader,gradereport_grader]
+ 2.7 en [summarygraderleft,gradereport_grader]
+ 2.7 en [summarygraderright,gradereport_grader]