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
The intention here was to change the function so that a different modal can be selected by passing a selector to the getModal function, i.e. `getModal('.upload-modal')` will return the element that has both the `.modal` and the `.upload-modal` class. 

This was done because of the the changing of an asset license uses a modal to display the licenseSelector, and that page already has a modal for uploading assets to your course. With the current function, adding a second element with the `.modal` class will cause both to be selected by `getModa()l`.