Documentation to help developers use the following classes:
- utm.mixin
- rating.mixin
- website.published.mixin
- website.seo.metadata
- mail.thread
- mail.alias.mixin

After careful consideration, the ir.needaction.mixin was
not included in this doc page since it is no longer displayed
anywhere and will be dropped quite soon.

* opt-in toc navification
* unhide index toctree, it's now back to a list of documents
* remove text thing

also pass PNGs through crusher, turns out dot produces pretty terrible PNGs

bzr revid: xmo@openerp.com-20121004074610-o2wk9nspzgqjj4y1

bzr revid: xmo@openerp.com-20121002172724-p93ku1ebo4m7gu9e