Dirble is no longer available and per the author/old-owner, will probably not
be coming back.
This commit removes the configuration option and the code used to access
dirble. Everything else still appears to be functional.
re: https://dev.to/confact/what-happened-with-dirble-k3g
init script: depend on $remote_fs instead of $local_fs. Reason: /usr can
be mounted a remote filesystem. Also depend on mpd (instead of $mpd,
which doesn't seem to exist.. at least on my system)
Also provide a default config (which should be installed as
/etc/default/ympd)
This commit makes the systemd unit file as well as the init script load
values from this configuration file so the user can change ympd settings
easily when running it as a service.
