dashboard: use activity icons in templates

fixes #261

circle/dashboard/templates/dashboard/instanceactivity_detail.html

@@ -4,7 +4,7 @@
 {% block content %}
 <div class="body-content">
   <div class="page-header">
-    <h1>
+    <h1><i class="fa fa-{{icon}}"></i>
         {{ object.instance.name }}:
             {% if user.is_superuser %}
             {{object.readable_name.get_admin_text}}

circle/dashboard/templates/dashboard/vm-detail/_activity-timeline.html

@@ -5,7 +5,7 @@
 {% for a in activities %}
 <div class="activity{% if a.pk == active.pk %} activity-active{%endif%}" data-activity-id="{{ a.pk }}">
   <span class="timeline-icon{% if a.has_failed %} timeline-icon-failed{% endif %}">
-  <i class="fa {% if not a.finished %}fa-refresh fa-spin {% else %}fa-plus{% endif %}"></i>
+  <i class="fa {% if not a.finished %}fa-refresh fa-spin {% else %}fa-{{a.icon}}{% endif %}"></i>
 </span>
 <strong{% if a.result %} title="{{ a.result.get_user_text }}"{% endif %}>
   <a href="{{ a.get_absolute_url }}">