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

Hackathon with @frrrances and @mhoeber 

@dmitchell Please review the Python/JS code. Much of it should be familiar to you. :) Mark will be updating the user-visible Strings, but all functionality is working.

Depends on https://github.com/edx/XBlock/pull/223 (which has already been merged).
Just a thought and not something that needs to be addressed now. I wonder if we should be grouping like-minded settings together, rather than sorting everything alphabetically. It would be nice to have all the discussion settings together, for example.

Really, what we need is a discussion xblock that has an admin view for all of its settings. :-) It is crazy that every block has to store its settings on the course block...