Non-semantic forms for editors

![pia7y](https://f.cloud.github.com/assets/224531/1506208/2046b3ca-4910-11e3-9d90-4dbc1daa3efe.jpg)

This lets you use Chameleon Forms within a partial, an editor template or a view template, by using `BeginChameleonEditor`, which just skips the `<form>` markup generation.