add generic service file

octoprint_generic.service

@@ -0,0 +1,17 @@
+[Unit]
+Description=The snappy web interface for your 3D printer
+After=network.online.target
+Wants=network.online.target
+
+[Service]
+Environment="HOST=127.0.0.1"
+Environment="PORT=NEWPORT"
+Environment="BASEDIR=OCTOCONFIG/.NEWINSTANCE"
+Environment="CONFIGFILE=OCTOCONFIG/.NEWINSTANCE/config.yaml"
+Environment="EXEC=OCTOPATH"
+Type=simple
+User=OCTOUSER
+ExecStart=${EXEC} serve --config=${CONFIGFILE} --basedir=${BASEDIR} --host=${HOST} --port=${PORT}
+
+[Install]
+WantedBy=multi-user.target