Add systemd unit files for ZFS startup

This adds systemd unit files replacing the functionality offered by
the SysV init script found in etc/init.d.

It has been developed and tested on Fedora 19, Fedora 20
and openSuSE 13.1.

Four unit files and one target are offered.

zfs-import-cache.service:
    Import pools from /etc/zfs/zpool.cache. This unit will wait for
    udev to settle.
zfs-import-scan.service:
    Import pools by scanning /dev/disk/by-id for zvols. This unit will
    only run if /etc/zfs/zpool.cache is not present. This unit will wait
    for udev to settle
zfs-mount.service:
    Mount ZFS native filesystems. It contains a dependency to be loaded
    before local-fs.target.
zfs-share.service:
    Share NFS/SMB filesystems. This unit contains a dependency that
    will cause it to be restarted whenever the smb or nfs-server unit
    is restarted, restoring the shares added.
zfs.target:
    This target pulls in the other units in order to start ZFS. It's
    the only unit that can be enabled/disabled, all other services
    are static and pulled in by dependencies. It will honour zfs=off
    and zfs=no options on the kernel command line.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #2108

etc/modules-load.d/.gitignore

@@ -0,0 +1 @@
+*.conf

etc/modules-load.d/Makefile.am

@@ -0,0 +1,13 @@
+modulesload_DATA = \
+	$(top_srcdir)/etc/modules-load.d/zfs.conf
+
+EXTRA_DIST = \
+	$(top_srcdir)/etc/modules-load.d/zfs.conf.in
+
+$(modulesload_DATA):
+	-$(SED) \
+		-e '' \
+		'$@.in' >'$@'
+
+distclean-local::
+	-$(RM) $(modulesload_DATA)

etc/modules-load.d/zfs.conf.in

@@ -0,0 +1 @@
+zfs