This option has Dovecot only return directories in LIST commands, which
is a necessary workaround because of how our home and maildir locations
are the same, which sometimes has extraneous files (such as Sieve
scripts) appear in IMAP directory listings.
We should eventually move away from this unified location, but doing so
requires careful planning and migration.
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.
