Add instance configuration into a rawConfig instance property

I am using this bundle to generate several CKEditor inputs. When I am doing it server-side, all is correct and easy to use. Yet, I have to generate client-side some WYSIWYG textareas, to deal CRUD with Javascript collections.

This PR simply introduces a third variable for storing server generated configuration. This way, it is far easier to get default configuration as required by `replace` function, based on a pre-existing item. Indeed, the `CKEDITOR.instances["myinstance"].config` is a `prototypedCopy`, which is not valid for `replace` method.