Layer configuration of the system daemon with a custom conf and a default conf
This fixes the 7th item at #180.
Quoting the main commit:
The conf file at datadir:
* Is the default configuration
* Is installed
* Has lower priority
The conf file at sysconfdir:
* Is the custom configuration
* Isn't installed
* Has higher priority
If the sysadmin wants to modify/overwrite the default configuration,
the custom conf file will need to be generated. This happens automatically
when using grdctl --system [...].