sort outcome gradebook by student name

fixes CNVS-10634

test plan:
  * as a teacher, navigate to a course with the outcome
    gradebook enabled;
  * verify that rows are student by student sortable name.

Change-Id: Ie79872c6a0a7f04118fcbc95da2f17eb8ba3d703
Reviewed-on: https://gerrit.instructure.com/29003
Reviewed-by: Zach Pendleton <zachp@instructure.com>
Product-Review: Zach Pendleton <zachp@instructure.com>
QA-Review: Zach Pendleton <zachp@instructure.com>
Tested-by: Jenkins <jenkins@instructure.com>