FIX for issue 619, fixed sorting on columns that contain html

Fixed improper sorting of columns that contained html with text (ie: checkboxes). Overwritten sort method inequality was reversed and expression was missing logic to change returned value to either 1 or -1. Affected columns: Assignments->Graders->Groups->graders column, Assignments->Graders->Criteria->graders column, Assignments->Groups->All Groups->members column, Assignments->Groups->Valid->members column . (Issue #619)