Splitting app.js into two files. Changing angular braces style in CSS. Adding the Superstep buttons.

Haven't made any functional changes. Only split the js file and other cosmetic changes mentioned above. Criterion for splitting - Public-like methods that are important and expected to be called from the client (index.html, or any other page instantiating the editor object), like restart(), @constructor, getMessagesSentByNode etc... are placed in editor.core.js. Other methods that used internally by the core methods are placed in editor.utils.js. Both files are now  about 400 lines each (even split!).