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=1f70c8582d18b3af29be789cac7a8063d26179f3
http://github.com/moodle/moodle/commit/1f70c8582d18b3af29be789cac7a8063d26179f3
+ 2.8 en [summarygrader,gradereport_grader]