Creative Commons Licensing for edX

This PR adds Creative Commons Licensing to the Open edX Platform.

Review tickets
T&L https://openedx.atlassian.net/browse/TNL-195
UX https://openedx.atlassian.net/browse/UX-948
So, most of the time this function will return an HTML string, but sometimes, it just returns text? That's bizarre. Even if that's the behavior that you actually want, this text needs to be internationalized.