Add LRS integration

[npaun]

Problem:

• You'd like to be notified when new LRS course recordings are available. Possibly mirror them too.
• You'd like to be able to download LRS recordings for a certain day, using a less painful UI.
• Some LRS courses are public (in one of lrs.mcgill.ca, cool.mcgill.ca, bcooltv.mcgill.ca), some are listed only in myCourses

Solution:

• Minervac could find the right LRS course ID from your myCourses, or use a mapping of public IDs.
• It could then show a report from the feed, generate the right download link and send email messages.

Implementation

• Once the correct mapping is found, a RSS feed is generated.
• RSS can be properly parsed, and a small report could be made.
• URLs could be computed by searching the RSS according to simple criteria. 'Last Friday', etc.

[npaun]

Partially implemented with grablrs.py, which allows users to download lecture recordings by URL.
Still need to implement the listings for various enrolled/public courses.