WIP: fixes for IE9

Some fixes to avoid failures in IE9.

* patterns/structure/views/app: Explicitly wrap self.dropzone in jQuery. This prevents the following error in IE9:
  Object doesn't support property or method 'on'
* patterns/dropzone: use self.$dropzone (=wrapped in jQuery), not self.dropzone, to call "on" on. Fixes same error as above

NOTE: the dropzone pattern is currently being refactored! Merging these changes need to wait for those changes.