[Embed] Add UI element and fix some bugs

plugins/Embed/templates/embed/embedView.html.twig

@@ -1,7 +1,14 @@
 <article class="h-entry embed">
     <header>
-        {% if attributes != false %}
-            <img class="u-photo embed" width="{{attributes['width']}}" height="{{attributes['height']}}" src="{{attributes['src']}}" />
+        {% if attributes['has_attachment'] != false %}
+            {% set thumbnail_parameters = {
+                'id': embed.getAttachmentId(),
+                'w': attributes['width'],
+                'h': attributes['height']
+            } %}
+            <img alt="{{embed.getTitle() | escape}}" class="{{attributes['class']}}"
+                 width="{{attributes['width']}}" height="{{attributes['height']}}"
+                 src="{{ path('attachment_thumbnail', thumbnail_parameters) }}" />
         {% endif %}
         <h5 class="p-name embed">
             <a class="u-url" href="{{link.getUrl()}}">{{embed.getTitle() | escape}}</a>
@@ -28,6 +35,6 @@
         </div>
     </header>
     <div class="p-summary embed">
-        {{ embed.getHtml() | escape }}
+        {{ embed.getDescription() | escape }}
     </div>
 </article>