[simple theme] rework select; add safesearch to search and replace / with › in article url

* rework selection UI in pref (fix based on: https://github.com/twelsby/searx/commit/78643e9f43a103c523f112e9f3ce26a5c7bb3a0f)
* moved search filters underneath categories
* cut params from url and replace / with ›
* make h3 and url in article bigger
* add safe search select to search filter (this will not override settings and only be valid while on result page in a session)
* make search form button not overlap each other when js is disabled
* 1rem padding around preview image and thumbnail in default article template

searx/templates/simple/categories.html

@@ -13,6 +13,7 @@
 }  -%}
 <div id="categories" class="search_categories">{{- '' -}}
     <div id="categories_container">
+        {%- if display_tooltip %}<div class="help">{{ _('Click on the magnifier to perform search') }}</div>{% endif -%}
         {%- for category in categories -%}
         <div class="category"><input type="checkbox" id="checkbox_{{ category|replace(' ', '_') }}" name="category_{{ category }}"{% if category in selected_categories %} checked="checked"{% endif %}/>
             <label for="checkbox_{{ category|replace(' ', '_') }}" class="tooltips">
@@ -21,6 +22,5 @@
             </label>
         </div>
         {%- endfor -%}
-        {%- if display_tooltip %}<div class="help">{{ _('Click on the magnifier to perform search') }}</div>{% endif -%}
     </div>{{- '' -}}
 </div>