Fix issue where VHOST was not properly being set

The URL file is being rewritten on every deploy by `dokku deploy` and thus that file was incorrect. Instead, we just reuse the old logic from the nginx-vhosts plugin to handle creation of the VHOST file
Delete the VHOST file, not the URL file, when NO_VHOST is set

The URL file is useful for understanding what port docker decided to host our app internally on.
Use a one-liner for the "Configuring" echo statement
Do not overwrite URL file
Use updated VHOST file instead of URL file when outputting the current URL to an app

Note that this may include more than one URL to an app