Enable Presentation of Windows Shadow Copies

I use ZFS snapshots on many of the datasets.

Use the following configuration to present these snapshots to Windows clients as shadow copies.

This will only show the "frequent" snapshots (i.e: at the time of writing, every 15 minutes for the last 24 hours).

    # enable shadow copies
    vfs objects = shadow_copy2
    shadow:snapdir = .zfs/snapshot
    shadow:snapdirseverywhere = yes
    shadow:sort = desc
    shadow:format = zfs-auto-snap_frequent-%Y-%m-%d-%H%M
    shadow:localtime = yes