Added allowed_content and custom editor css support to configuration and bolt.js.
After update to ckEditor 4.1 my custom HTML containing Elements like <section> was detroyed.

However setting `allowed_content` to `true` avoids breaking my markup.
The other change allows users to style ckEditor contents with a CSS file from their theme.

	modified:   app/config/config.yml.dist
	modified:   app/view/_footer.twig
	modified:   app/view/js/bolt.js