webui: add help text for vm

one/templates/box/vm/box.html

@@ -7,6 +7,21 @@
     {% trans "Virtual machines" %}
 {% endblock title %}
 
+{% block boxhelp %}
+<div class="boxhelp">
+    <div class="icon">
+        <img src="/static/icons/information-frame.png" alt="{% trans "Help" %}" />
+    </div>
+    <div class="boxhelp-box">
+        <p>{% blocktrans %}This is the list of your running virtual machines.{% endblocktrans %}</p>
+        <p>{% blocktrans %}You can launch a new VM instance if it is shared by
+        a teacher for one of your groups.{% endblocktrans %}</p>
+        <p>{% blocktrans %}Please note, that users and shares both have a limit
+        of launchable instances.{% endblocktrans %}</p>
+    </div>
+</div>
+{% endblock %}
+
 {% block content %}
 <ul class="vm-list entry-list">
     {% if instances %}