Add tagged services for import

- list services in /import
- add url to import service
- ImportBundle routing are now prefixed by /import
- optimize flush in each import (flushing each 20 contents)
- improve design of each import
- add more tests

src/Wallabag/ImportBundle/Resources/views/Import/index.html.twig

@@ -1,15 +1,19 @@
 {% extends "WallabagCoreBundle::layout.html.twig" %}
-{% block title %}{% trans %}import{% endtrans %}{% endblock %}
+{% block title %}{% trans %}Import{% endtrans %}{% endblock %}
 
 {% block content %}
-
 <div class="row">
     <div class="col s12">
         <div class="card-panel settings">
             {% trans %}Welcome on wallabag importer. Please select your previous service that you want to migrate.{% endtrans %}
             <ul>
-                <li><a href="{{ path('import_pocket') }}">Pocket</a></li>
-                <li><a href="{{ path('import_wallabag_v1') }}">Wallabag v1</a></li>
+                {% for import in imports %}
+                    <li>
+                        <h5>{{ import.name }}</h5>
+                        <blockquote>{{ import.description|raw }}</blockquote>
+                        <p><a class="waves-effect waves-light btn" href="{{ path(import.url) }}">Import contents</a></p>
+                    </li>
+                {% endfor %}
             </ul>
         </div>
     </div>