Resolve "[External link widget] Make icon clickable"

Closes #710 (closed)

aleksis/core/templates/core/dashboard_widget/external_link_widget.html

 <div class="card">
         <div class="card-image">
-                <img src="{{ icon_url }}" alt="{{ title }}" />
+                <a href="{{ url }}"><img src="{{ icon_url }}" alt="{{ title }}" /></a>
         </div>
         <div class="card-action">
                 <a href="{{ url }}">{{ title }}</a>