Ability to get a course grade for a single student regardless of whether course grades are released

From Payten Giles on October 16, 2015 0:38

Required for https://github.com/steveswinsburg/gradebookNG/pull/247.

In dynamically updating a student's course grade when a score changes, the current endpoint returns 'null' if the course grades are configured to be not released to students. It'd be great to have the ability to pull back the latest course grade for a single student, also formatted accordingly to the Gradebook settings.

Copied from original issue: steveswinsburg/gradebookNGGIT2-266