Add terms on client side.

I know that this should be proposed as a patch in mozilla-central.
I put it here to work on the patch and then I will make the appropriate patch to mozcentral.

 - [x] HTML / Ajax term loader based on the Accept Language of the browser (given back by loop-server)
 - [x] Extract ToS from legal-docs using grunt and bower.
Should this file be checked in?
I always get confused when we check in source .scss files and then generated .css files. I don't want people to make quick edits to the *.css file and then we lose them all because the grunt-sass task overwrites it during build.