This enables the `web_directory` and `web_url` options for Spectrum,
which has media shared by legacy protocol buddies be re-hosted by
Spectrum, and shared by a dedicated volume.
This, in turn, is served by the `nginx-serve-volume@spectrum-media`
service, which is intended to be proxied under the same host used for
Prosody. Documentation for the integration will be added in future
commits.
This commit contains a fairly large diff for a fairly small change:
moving the `config/common` directory to `host/base` to better reflect
its intended use, and promoting `config/service` to the root directory.
These changes unlock some improvements in `coreos-home-server-update`
processes, which will (assuming `/etc/coreos-home-server/base` exists)
keep host-wide systemd services in sync in addition to service-specific
ones.
Changes have been make to the `Makefile` and a few other places where
`config/common` was referenced, but most of this work is renames that
are not intended to break compatibility with new or running servers.
