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
Why are you returning a HTML string? If you want to return a DOM object that represents an image tag, jQuery has very nice constructors for creating DOM objects:
```js
var img = $("<img>", {src: img_url + imgSize + ".png"})
```