[enh] displaying shortcuts at engines page

searx/templates/engines.html

     <table style="width: 80%;">
         <tr>
             <th>{{ _('Engine name') }}</th>
+            <th>{{ _('Shortcut') }}</th>
             <th>{{ _('Category') }}</th>
         </tr>
     {% for (categ,search_engines) in categs %}
             {% if not search_engine.private %}
             <tr>
                 <td>{{ search_engine.name }}</td>
+                <td>{{ shortcuts[search_engine.name] }}</td>
                 <td>{{ _(categ) }}</td>
             </tr>
             {% endif %}

searx/webapp.py

 
     List of all supported engines.
     """
-    global categories
-    return render('engines.html', categs=categories.items())
+    return render('engines.html',
+                  categs=categories.items(),
+                  shortcuts={y:x for x,y in engine_shortcuts.items()})
 
 
 @app.route('/preferences', methods=['GET', 'POST'])