Support multilanguage group names in assign activity

In a course in which you possess teacher privileges:

1. Create groups with names containing multilanguage strings, e.g. "<span class="multilang" lang="de">Abgabegruppe</span> <span class="multilang" lang="en">Submission group</span> A"
2. Create an assignment activity and configure it as follows:
   • Ensure that file type submission is selected. 
   • Ensure that feedback type "Annotate PDF" is selected.
   • Ensure that submission is available for groups only and that a group is required to make a submission.
3. Ensure that the course has at least one participant.
   • Ensure that said participant is a member of a valid submission group (i.e. one with a multilanguage string in its name)!
   • Ensure that said participant has submitted an assignment in the previously created activity.
4. Browse to the activity and click on the "Grade" button.
   • Verify whether the grading window loads properly or throws an Error.

In a course in which you possess teacher privileges:

1. Create groups with names containing other HTML strings, e.g. "<script>Submission group</script> <b>A</b>"
2. Ensure that those HTML tags are filtered out. (e.g. by editing that group again and checking its name)