reintroduce allow_functionality subscription

 * contains rules needed for the top100 websites to work as expected
 * top100 list from http://www.alexa.com/topsites
 * these rules are not suitable for allow_sameorg (cross-site requests from/to different organizations)
 * add back allow_functionality entry in official.json subscriptions list
 * fixes RequestPolicyContinued#9
@ansell well spotted. `assetroot.s3.amazonaws.com` should be allowed from `bitbucket.org`. I visited https://bitbucket.org/Svedrin/mumble-django/ and didn't notice the missing logo.