- If runlevel isn't set (at all) then use "default". For
most systems that do not use multiple runlevels, this
simplifies the configuration to just a list of service names
to add or delete.
- Document the functions some more
- Only "state" (i.e. action) "add" and "del" make sense,
avoid calling rc-update for other keys (e.g. typo's).
This matches the documentation, although there might be
other actions that make sense (see also services-systemd,
with its enable, disable and mask actions).
