Author: Michael Hawkins
MDL-68612 user: Participants filter row accessibility improvements
More clearly defining each filter row and its ability to remove
filter selections for screen readers.
http://git.moodle.org/gw?p=moodle.git;a=commit;h=3d60881d5d7e18a549dcf39f19c122f28336e7d3
http://github.com/moodle/moodle/commit/3d60881d5d7e18a549dcf39f19c122f28336e7d3
+ 3.9 en [clearfilterselection,core_user]
+ 3.9 en [filterrowlegend,core_user]