Should fail compilation when default location created for vhost without other required parameters

[3flex]

When vhost resource is created a default location is automatically created for the vhost by default. However, if the user hasn't set www_root, proxy, fastcgi, or location_custom_cfg configuration on the vhost as well the location will be created with an invalid configuration.

There should be an error message in this case so the user knows what to do. See #446

[wyardley]

This error does now exist.