refactor: drop web installer in favor of setup via cli

This makes the installation a bit more secure by ensuring a user does not accidentally expose a way for unauthorized users to add new ssh keys to the system.

Additionally, this removes the extra HOSTNAME file to make the initial install process easier (that file was not modifiable by any dokku commands.

Closes #2247

docs/getting-started/install/dreamhost.md

@@ -180,7 +180,6 @@ apt:
         -----END PGP PUBLIC KEY BLOCK-----
 
   debconf_selections:
-    web:      dokku dokku/web_config boolean false
     vhost:    dokku dokku/vhost_enable boolean true
     # set the domain name of the new Dokku server
     hostname: dokku dokku/hostname string $YOUR_FULL_QUALIFIED_DOMAIN