This adds a simple configuration for sending snapshots to a remote
system using zfs-replicate that ties into the autoSnapshot settings
already present in services.zfs.autoSnapshot.
Without fcrontab being setuid, every attempt by an user in the fcron
group to edit their own crontab (via `fcrontab -e`) results in the
following error:
```
2018-05-06 11:29:07 ERROR could not change euid to 273: Operation not permitted
2018-05-06 11:29:07 ERROR fcron child aborted: this does not affect the main fcron daemon, but this may prevent a job from being run or an email from being sent.
```
Adding setuid by hand has resolved this issue and aligns with the way
fcrontab is installed on other distributions.
Alex Brandt