Workaround for galleria and videos

It looks like galleria's video tag in json support only external
provider (youtube etc.). So instead this shows an empty image and on top
a layer with the html video tag.

sigal/themes/galleria/templates/index.html

@@ -152,7 +152,8 @@
         image: "{{ media.filename }}"
         {% endif %}
         {% if media.type == "video" %}
-        video: "{{ media.filename }}"
+        image: "{{ theme.url }}/img/empty.png",
+        layer: "<video controls><source src='{{ media.filename }}' type='{{ media.mime }}' /></video>"
         {% endif %}
       },
       {% endfor %}