[fix] ordered categories in preferences - closes #258

searx/templates/courgette/preferences.html

                 <th>{{ _('Category') }}</th>
                 <th>{{ _('Allow') }} / {{ _('Block') }}</th>
             </tr>
-        {% for (categ,search_engines) in categs %}
-            {% for search_engine in search_engines %}
+        {% for categ in categories %}
+            {% for search_engine in engines_by_category[categ] %}
 
                 {% if not search_engine.private %}
                 <tr>

searx/templates/default/preferences.html

             <th>{{ _('Category') }}</th>
             <th>{{ _('Allow') }} / {{ _('Block') }}</th>
         </tr>
-    {% for (categ,search_engines) in categs %}
-        {% for search_engine in search_engines %}
+    {% for categ in categories %}
+        {% for search_engine in engines_by_category[categ] %}
 
             {% if not search_engine.private %}
             <tr>

searx/templates/oscar/preferences.html

 
             <!-- Nav tabs -->
             <ul class="nav nav-tabs nav-justified hide_if_nojs" role="tablist" style="margin-bottom:20px;">
-                {% for (categ,search_engines) in categs %}
+                {% for categ in categories %}
                 <li{% if loop.first %} class="active"{% endif %}><a href="#tab_engine_{{ categ|replace(' ', '_') }}" role="tab" data-toggle="tab">{{ _(categ) }}</a></li>
                 {% endfor %}
             </ul>
 
             <!-- Tab panes -->
             <div class="tab-content">
-                {% for (categ,search_engines) in categs %}
+                {% for categ in categories %}
                 <noscript><label>{{ _(categ) }}</label>
                 </noscript>
                 <div class="tab-pane{% if loop.first %} active{% endif %} active_if_nojs" id="tab_engine_{{ categ|replace(' ', '_') }}">
                     <div class="container-fluid">
                     <fieldset>
-                    {% for search_engine in search_engines %}
+                    {% for search_engine in engines_by_category[categ] %}
                         {% if not search_engine.private %}
                             <div class="row">
                                 {% if not rtl %}

searx/webapp.py

                   current_language=lang or 'all',
                   image_proxy=image_proxy,
                   language_codes=language_codes,
-                  categs=categories.items(),
+                  engines_by_category=categories,
                   blocked_engines=blocked_engines,
                   autocomplete_backends=autocomplete_backends,
                   shortcuts={y: x for x, y in engine_shortcuts.items()},