Users in the `prosody_user` and `prosody_admin` groups will be granted
access to Prosody (as regular users and administrators, respectively),
making this a more flexible solution compared to IMAP.
This brings a number of changes and improvements, and moves from MariaDB
to SQLite for storage, which requires manual migration for pre-existing
deployments using `prosody-migrator`.
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.
