Add className to a CKEditor.dialog instance

[Pierre Baron]

Hello,

When creating a new plugin, we almost always need to use a dialog instance. And maybe sometimes, we need to override default ckeditor style. In order to give all liberty of the theme of Ckeditor to the user, it would be a great idea to add a className attribute on the dialog configuration, so that plugin developers can add their own css without overriding everything else.

[Jakub Ś]

Currently there is only possibility to get class used by all dialogs and user can't customize styles for one particular dialog. Ability to add class to specific dialog would allow user customizing styles for one particular dialog he chooses.