Added an invokesuper attr to setters and methods to allow control over w...

...hen super is invoked.
One potential issue is that coffeescript uses the method name 'super' to call super. So, we will probably need to change this in the CS compiler, e.g. transform super() -> $$$super$$$(), compile to coffeescript, then $$$super$$$() -> super() again. I'm happy to do this as a follow up change, please file a pivotal for this if you don't get to it.