Display warnings when insufficient package of CKEditor is detected

Due to zillions of reports about missing buttons it would be probably better to display an information in the administration area, maybe somewhere close to the Drag&Drop toolbar configuration tool about a possibly invalid package of CKEditor used, which may not contain all the buttons offered by in the administration section.

The question is how to easily detect missing buttons, especially if we have to deal with custom builds.
Probably the easiest option is to check "CKEDITOR.config.plugins" in ckeditor.js and then check config.js for the existence of config.removeButtons in config.js.

A hardcoded mapping between plugins and buttons will help in finding which buttons are not available.

We cannot suddenly disable unavailable buttons in the D&D tool in the administration area, because an unaware user can overwrite the old library (e.g. 3.6.6) with 4.1 standard, without even knowing what's going on. In such case his toolbar configuration with buttons that are temporarily unavailable should not be lost.