Rather than require a heavy chown operation across various paths, just chown the files already in the built image during the release process. This ensures we can skip not-only the chown process during the container start that herokuish injects, but also the one that Dokku runs which modifies mounted container paths as well during the pre-deploy.
Note that users will need to ensure any mounted volumes don't have permissions reset by other processes or containers won't be able to access them.
This change makes interacting with port mappings more clear - folks might previously set the port mapping to the proxy type or vice-versa.
The existing proxy:ports* commands still exist but will show a deprecation warning for a single minor release.
The URLS file is no longer necessary as urls are now generated directly from the app VHOST file.
This also moves all the url generation logic to the domains plugin.
