CKEditor youtube plugin: upgrade to latest version

The latest integration of the CKEditor youtube plugin from origin [1] to our branch [2] dates from May 23, 2014, so any work in the upstream is not in our distribution.

Shall we update to latest version, currently 2.0.1?
See also section "Updating an external plugin" [3]

[1] https://github.com/fonini/ckeditor-youtube-plugin
[2] https://github.com/onehippo/ckeditor/tree/youtube/plugin
[3] https://github.com/onehippo/ckeditor#updating-an-external-plugin