Make a couple simple improvements to some datagrids.

This makes a couple changes to the "Submitters" and "Groups" datagrids. To
start, I've renamed "Submitters" to "Users". I've also switched the order of
"Users" and "Groups". Finally, I've renamed the "Pending Reviews" column to be
"Open Review Requests".

Testing done: Looked at the changed datagrids.

Reviewed at https://reviews.reviewboard.org/r/5417/
Add the students to the AUTHORS file.

The upcoming beta has contributions from a number of our students, so we
want to add them to the list of contributors.