nginx: normalize installation (docs and script)s over all distros

This is the revision of the documentation about the varous nginx installation
variants.  It also implements the nginx installation scripts for morty and
filtron.

Signed-off-by: Markus Heiser <markus.heiser@darmarit.de>

docs/admin/filtron.rst

@@ -158,6 +158,12 @@ of:
 Route request through filtron
 =============================
 
+.. sidebar:: further reading
+
+   - :ref:`filtron.sh overview`
+   - :ref:`installation nginx`
+   - :ref:`installation apache`
+
 Filtron can be started using the following command:
 
 .. code:: sh
@@ -171,15 +177,24 @@ Use it along with ``nginx`` with the following example configuration.
 
 .. code:: nginx
 
-   location / {
+   # https://example.org/searx
+
+   location /searx {
        proxy_pass         http://127.0.0.1:4004/;
 
        proxy_set_header   Host             $http_host;
+       proxy_set_header   Connection       $http_connection;
        proxy_set_header   X-Real-IP        $remote_addr;
        proxy_set_header   X-Forwarded-For  $proxy_add_x_forwarded_for;
        proxy_set_header   X-Scheme         $scheme;
+       proxy_set_header   X-Script-Name    /searx;
    }
 
+   location /searx/static {
+       /usr/local/searx/searx-src/searx/static;
+   }
+
+
 Requests are coming from port 4004 going through filtron and then forwarded to
 port 8888 where a searx is being run. For a complete setup see: :ref:`nginx
 searx site`.