Enables LMS to handle deprecated URLs

LMS-2651
I also include these in settings for lms/envs/common.py.

At first I tried just keeping these variables in the respective urls.py files, but it turns out common has a few places that use the COURSE_ID_PATTERN regex, and the most "central" place I could think of for keeping that information were the settings files.  If there's someplace I could stash these so that two separate settings files don't have the same information, I'd be happy to hear it