refactor studio and composer into modules

/to: @anthonyettinger 
/cc: @bajtos 

- removed the app module
- split it up into studio and composer
- moved GlobalExceptionView to ComposerExceptionView

Is there a way how to move this `resolve` code into composer module? The studio module should not need to know these details.

If the ui-router does not provide an easy way for that, then we can leave it as it is now.

BTW in an ideal world, the studio module should provide the `$stateProvider` configuration. That way you don't have to touch the studio module while working in the composer module.

```js
Composer.config(function($stateProvider) {
  $stateProvider.state('composer', {
       url: '/composer',
       // templateUrl, controller, resolve, etc.
  });
});