Get rid of WAMain and subclasses

[GoogleCodeExporter]

Let's specify an initial continuation for the Application instead of a Main 
class... simpler and just as effective.

Since we'll end up creating a continuation that creates and sets up a root 
presenter, this will also provide a better way of starting a new "render loop". 
Whee!

Original issue reported on code.google.com by jfitz...@gmail.com on 23 Aug 2011 at 3:41