Lilac: Remote gradebook & Canvas cherry-picks

[umarmughal824]

fixes #255

Cherry-pick the following commits into one commit and test that it works on the mitx/lilac branch.

(most recent at the top) 608828d e630376 e52d609 b331778 697ce49 1374507 63ceb85 ca3a1a6

I don't know how to test it but after making all these changes, my devstack is still functional. I had faced some import issues that I have fixed in the last commit to make it functional.

Screenshots

[umarmughal824]

@pdpinch I have addressed the feedback so that's ready for review again

@blarghmatey here is the isolated PR for that https://github.com/mitodl/edx-platform/pull/257

[blarghmatey]

Looks good to me