[mod] migrate all key-value.html templates to KeyValue type

The engines now all use KeyValue results and return the results in a
EngineResults object.

The sqlite engine can return MainResult results in addition to KeyValue
results (based on engine's config in settings.yml),

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

searx/templates/simple/result_templates/key-value.html

@@ -1,11 +0,0 @@
-<table>
-    {% for key, value in result.items() %}
-    {% if key in ['engine', 'engines', 'template', 'score', 'category', 'positions', 'parsed_url'] %}
-        {% continue %}
-    {% endif %}
-    <tr>
-        <td><b>{{ key|upper }}</b>: {{ value }}</td>
-    </tr>
-    {% endfor %}
-</table>
-<div class="engines">{% for engine in result.engines %}<span>{{ engine }}</span>{% endfor %}</div>{{- '' -}}