Use Croogo.bootstrapComplete event to start editor setup

Since `Wysiwyg.actions` has been setup by every plugin bootstrap.php,
attaching helpers now does not depend on plugin load order.

Closes croogo/croogo#409
Implement checkDirty() and resetDirty()
Support for preventing an element becoming a wysiwyg by adding a class
Merge branch '2.0'

* 2.0:
  Support for preventing an element becoming a wysiwyg by adding a class
  Implement checkDirty() and resetDirty()
  Use Croogo.bootstrapComplete event to start editor setup