Trunk dialogs integrated with stars/dialog buttons etc.
Pre/Post/Pre&Post/None type of interstitials
common.css created
generated blocks instead of images for interstitials
general updates to text and style.

Changelist carried over from svn https://codereview.appspot.com/13319043/
Applied Ellen's Suggestions
Applied Ellen's Suggestions
Updating template.soy
Removed incorrect jsdoc notation.
Merge pull request #13 from brokenairplane/mooc

Trunk dialogs integrated with stars/dialog buttons etc.