Added icons for controling beamer view (pan,zoom)

openslides/agenda/templates/agenda/overview.html

@@ -45,9 +45,9 @@
                 <input type="button" onclick="window.location.href='{% url item_overview %}';" value="{%trans 'No' %}">
             </em>
         </div>
+        <a class="beamer_edit" href="{% url beamer_bigger %}"><img src="/static/images/icons/zoom-in.png"></a> <a class="beamer_edit" href="{% url beamer_smaller %}"><img src="/static/images/icons/zoom-out.png"></a>
+        <a class="beamer_edit" href="{% url beamer_up %}"><img src="/static/images/icons/go-up.png"></a> <a class="beamer_edit" href="{% url beamer_down %}"><img src="/static/images/icons/go-down.png"></a> <br>
         {% endif %}
-        <a class="beamer_edit" href="{% url beamer_bigger %}">+</a> <a class="beamer_edit" href="{% url beamer_smaller %}">-</a> <br>
-        <a class="beamer_edit" href="{% url beamer_up %}">+</a> <a class="beamer_edit" href="{% url beamer_down %}">-</a> <br>
         <table id="menu-overview" class="agendatable">
             <tr>
                 <th style="width: 1px;">{% trans "Beamer" %}</th>