Make CKEditor part of standard release process

CKEditor includes the platform version, like 4.7.0-h12.4.0. That makes it difficult to work with using our current scripts. We have been manually setting up branches for each minor platform version, and they're internally inconsistent right now.

As a solution we suggest to undo the refactoring of our ckeditor fork:

• Move the 'config' module of our CKEditor fork back to the CMS.
• Move the frontend part of our hippopicker plugin back (which also moved from CMS to CKEditor fork) since it's closely related to Wicket code in the CMS.
• Let the Channel Manager depend on this new config module in the CMS.
• Change the versioning (and branching) of CKEditor to a hippo/4.9.x master with version number 4.9.2-h1.