add a (hidden) ./svg URL on workflows (fix #1663)

wcs/admin/workflows.ptl

@@ -527,7 +527,7 @@ class WorkflowStatusDirectory(Directory):
 
 class WorkflowPage(Directory):
     _q_exports = ['', 'edit', 'delete', 'newstatus', ('status', 'status_dir'), 'update_order',
-            'duplicate', 'export']
+            'duplicate', 'export', 'svg']
 
     def __init__(self, component):
         try:
@@ -588,6 +588,11 @@ class WorkflowPage(Directory):
         if not str(self.workflow.id).startswith(str('_')):
             self.get_new_status_form()
 
+    def svg(self):
+        response = get_response()
+        response.set_content_type('image/svg+xml')
+        return graphviz(self.workflow, include=False)
+
     def export(self):
         x = self.workflow.export_to_xml()
         indent(x)