Add 'force https' to manage domains

Add a Manage Domains or Manage SSL certificates checkbox that will add/remove htaccess code that forces the domain to be served via secure hosting, such as:

RewriteEngine On
RewriteCond %{SERVER_PORT} !^443$
RewriteRule ^(.*)$ https://EXAMPLE.COM/$1 [R=permanent]

The option should of course be inactive until there is a valid https configuration.