[enh] links to preferences

searx/templates/index.html

     {% include 'search.html' %}
     <p class="top_margin">
         <a href="/about" class="hmarg">about</a>
+        <a href="/preferences" class="hmarg">preferences</a>
     </p>
 </div>
 {% endblock %}

searx/templates/results.html

 {% extends "base.html" %}
 {% block title %}{{ q }} - {% endblock %}
 {% block content %}
+<div class="right"><a href="/preferences">preferences</a></div>
 <div class="small">
     {% include 'search.html' %}
 </div>