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/Pocket/index.html.twig

@@ -1,14 +1,16 @@
 {% extends "WallabagCoreBundle::layout.html.twig" %}
-{% block title %}{% trans %}import{% endtrans %}{% endblock %}
+{% block title %}{% trans %}Import > Pocket{% endtrans %}{% endblock %}
 
 {% block content %}
-
 <div class="row">
     <div class="col s12">
         <div class="card-panel settings">
-            {% trans %}You can import your data from your Pocket account. You just have to click on the below button and authorize the application to connect to getpocket.com.{% endtrans %}
+            <blockquote>{{ import.description|raw }}</blockquote>
+            <p>{% trans %}You can import your data from your Pocket account. You just have to click on the below button and authorize the application to connect to getpocket.com.{% endtrans %}</p>
             <form method="post" action="{{ path('import_pocket_auth') }}">
-                <input type="submit" value="Connect to Pocket and import data" />
+                <button class="btn waves-effect waves-light" type="submit" name="action">
+                    Connect to Pocket and import data
+                </button>
             </form>
         </div>
     </div>