Add systemd unit file and README.systemd explanation

Merged from https://github.com/koniu/recoll-webui/pull/55
Add a sample systemd script in examples and a README describing how to
integrate the standalone WebUI app with systemd.
Author: Rob Fair <fair.rob@gmail.com>

README.rst

@@ -52,6 +52,9 @@ There's some optional command-line arguments available::
     -a ADDR, --addr ADDR  address to bind to [127.0.0.1]
     -p PORT, --port PORT  port to listen on [8080]
 
+The standalone application can be configured to run automatically using
+systemd. See the file README.systemd.
+
 Run as WSGI/CGI
 ---------------
 

README.systemd

@@ -0,0 +1,77 @@
+Using the standalone WebUI application with systemd
+---------------------------------------------------
+This README describes how to configure systemd so that the 
+standalone WebUI application can run automatically as a systemd service.
+
+Before doing this, ensure that the standalone application runs OK 
+when run from the command line, and that it is *not* configured to
+be run as part of an existing web service, e.g. Apache.
+
+Systemd configuration script
+----------------------------
+A sample systemd configuration script for the WebUI application is
+in examples/recoll-webui.service. This assumes the following configuration:
+
+- The WebUI application runs as user 'recoll',  with the WebUI source located
+  in /home/recoll/recoll-webui.
+- The application should listen on the default IP address for the system.
+- The application uses port 8080.
+
+If any of these are different for your installation, change the
+configuration script accordingly.
+
+Installing the configuration script
+-----------------------------------
+The configuration script must be copied to the systemd directory
+and given the correct ownership/access . This can be done using:
+
+   $ sudo cp examples/recoll-webui /etc/systemd/system/recoll-webui
+   $ sudo chown root /etc/systemd/system/recoll-webui
+   $ sudo chmod 644 /etc/systemd/system/recoll-webui
+
+Starting the WebUI service
+--------------------------
+To start the WebUI service do:
+
+  $ sudo systemctl start recoll-webui
+
+This does a one-time start of the service. If you want to automatically start the  
+service at boot, also do:
+
+  $ sudo systemctl enable recoll-webui
+
+Checking the status of the WebUI service
+----------------------------------------
+Check the status of the WebUI service with:
+
+  $ sudo systemctl status recoll-webui
+
+If it is running you should see output similar to this:
+
+    recoll-webui.service - Recoll Search WebUI
+       Loaded: loaded (/etc/systemd/system/recoll-webui.service; enabled; vendor preset: disabled)
+       Active: active (running) since Fri 2016-10-07 08:46:00 EDT; 1 day 12h ago
+      Process: 16278 ExecStop=/bin/kill -SIGINT $MAINPID (code=exited, status=0/SUCCESS)
+     Main PID: 16281 (python)
+       CGroup: /system.slice/recoll-webui.service
+               └─16281 python /home/recoll/recoll-webui/webui-standalone.py -a myhost -p 8080
+
+This shows the status of the standalone application, along with the command line that
+was used. 
+
+Stopping the WebUI service
+--------------------------
+To stop the WebUI service do:
+
+    $ sudo systemctl stop recoll-webui
+
+To disable the service so it does not run at boot time do:
+
+    $ sudo systemctl disable recoll-webui
+
+Restarting the WebUI service
+----------------------------
+The WebUI configuration script is set to automatically restart the 
+standalone application if it fails. You can also manually restart it using:
+
+    $ sudo systemctl restart recoll-webui

examples/recoll-webui.service

@@ -0,0 +1,35 @@
+# SystemD script for running the standalong server as a daemon
+# Place this in /etc/systemd/system/recoll-webui.servivce
+# owned by root, mode 0644
+
+# This assumes the Recoll Web-UI is installed under
+# the path /home/recoll/recoll-webui, and runs against port 8080.
+# Change these below as needed.
+#
+[Unit]
+Description=Recoll Search WebUI
+
+After=network.target
+
+RequiresMountsFor=/home/recoll
+
+[Service]
+# Standalone server runs as the main job, default
+Type=simple
+
+# Run under user recoll
+User=recoll
+
+# Set listen port and address as needed.
+# %H is the current host name
+ExecStart=/home/recoll/recoll-webui/webui-standalone.py \
+	  -a %H \
+	  -p 8080
+
+ExecStop=/bin/kill -SIGINT $MAINPID
+KillMode=process
+
+Restart=on-failure
+
+[Install]
+WantedBy=multi-user.target