Remove the wpdialog plugin from TinyMCE

[azaozz]

Combining TinyMCE with jQueryUI is not a very good idea IMHO:

• TinyMCE has all the functionality to create dialogs which is native, more extended and seems more robust than jQuery UI.
• The reason why most dialog type scripts use an iframe is to remove any possibility of conflicts with the parent page. In out case such conflict might be introduced by a plugin that alters the edit screen.
• There were suggestions some time ago to stop using jQuery UI in WordPress admin and replace it with one of the other jQuery plugins with similar functionality that are a lot more concise and robust.