Added CKEditor support + fix WymEditor YouTube embed

WymEditor has an issue with embedded YouTube clips and requires the embed plug-in.  The embed plug-in has been recently updated to correct a fix in how it handles <object> tags, so the latest version of the embed should probably be included too in this package.

Also, I've refactored the code a bit to enable support for CKEditor.  I think CKEditor is a lot more intuitive to use, and it offers support for using the Django filebrowser plug-in, which depends on the grappelli app.  In any case, the documentation and code has been tested on my end.  Give it a try!