Remove 'enforce_www' 'enforce_no_www' options

These options were not used in any production sites, as this
redirection is best performed at the border (for example, in
sslloadbalancer-formula).

The redirect method, using $uri, was insecure, allowing header
injection.

With this in mind, less code FTW.
Merge pull request #18 from ministryofjustice/remove_www_redirs

Remove 'enforce_www' 'enforce_no_www' options