[imp] use layouts for tinyMCE

tinyMCE editor markup is output in the plugin. That means that is not possible to override it in templates (for example) or in component views if someday my JLaoyuts improvements get merged ( https://github.com/joomla/joomla-cms/pull/1419 )

This PR adds layouts to solve that issue.

Issue tracker:
http://joomlacode.org/gf/project/joomla/tracker/?action=TrackerItemEdit&tracker_item_id=32031