Ability to insert Youtube video

* First attempt, fixed width and height to minimal.
* Works with typical youtube URLs like
'http://www.youtube.com/watch?v=...'.
* Updates in en, el locales (video key). Needed for other locales.
* No changes made to underlying editor.
* Added functions in basic js file, that can be transfered in separate
file(s). Rake to dist pending.
changed default styling
youtube videos