[config] Include systemd service file (closes #213)

INSTALL

@@ -217,7 +217,10 @@ this and make the user a member of the group, for instance) and read/write
 permissions on the database location ($localstatedir/cache/forked-daapd by
 default).
 
-You'll need an init script if you want to start forked-daapd at boot. A simple
+If your system uses systemd then you might be able to use the service file
+included, see forked-daapd.service.
+
+Otherwise you might need an init script to start forked-daapd at boot. A simple
 init script will do, forked-daapd daemonizes all by itself and creates a
 pidfile under /var/run. Different distributions have different standards for
 init scripts and some do not use init scripts anymore; check the documentation

forked-daapd.service

@@ -0,0 +1,15 @@
+[Unit]
+Description=DAAP/DACP (iTunes), RSP and MPD server, supports AirPlay and Remote
+After=network.target
+
+[Service]
+ExecStart=/usr/sbin/forked-daapd -f
+
+# Restart, but not more than once every 10 minutes
+Restart=on-failure
+StartLimitBurst=2
+StartLimitInterval=600
+
+[Install]
+WantedBy=multi-user.target
+