Write out unique includes in element factories

Source/build/scripts/templates/ElementFactory.cpp.tmpl

Index: Source/build/scripts/templates/ElementFactory.cpp.tmpl
diff --git a/Source/build/scripts/templates/ElementFactory.cpp.tmpl b/Source/build/scripts/templates/ElementFactory.cpp.tmpl
index 4ed11eddbcbf442d525a8420413b53d3ec79a239..091b1b9d89b79445639d66554604edcd1a23940a 100644
--- a/Source/build/scripts/templates/ElementFactory.cpp.tmpl
+++ b/Source/build/scripts/templates/ElementFactory.cpp.tmpl
@@ -5,8 +5,8 @@
 #include "{{namespace}}ElementFactory.h"
 
 #include "{{namespace}}Names.h"
-{% for tag in tags|sort %}
-#include "core/{{namespace|lower}}/{{tag.interface}}.h"
+{% for tag in tags|groupby('interface') %}
+#include "core/{{namespace|lower}}/{{tag[0]}}.h"
 {% endfor %}
 {% if fallback_interface %}
 #include "core/{{namespace|lower}}/{{fallback_interface}}.h"