WIP: Display names, help text, and "deprecated" for Advanced Settings.

Hackathon with @frrrances and @mhoeber 

The last entry ("XQA Key") is deprecated.

Depends on https://github.com/edx/XBlock/pull/223
Note to reviewer: I could see no reason why this wrap of the save call exists. At one point, there was a potential of 2 chained calls, but we aren't using that functionality.