Add usable PCB_GROUP::GetItems() swig wrapper

(cherry picked from commit 9b58f50c68)

pcbnew/python/swig/pcb_group.i

@@ -1,6 +1,27 @@
 
 
-%include pcb_group.h
 %{
 #include <pcb_group.h>
 %}
+%include pcb_group.h
+
+%extend PCB_GROUP
+{
+    std::deque<BOARD_ITEM*> GetItemsDeque()
+    {
+        std::deque<BOARD_ITEM*> result;
+
+        const std::unordered_set<BOARD_ITEM*> items = $self->GetItems();
+
+        for(BOARD_ITEM* item: items)
+            result.push_back(item);
+
+        return result;
+    }
+
+    %pythoncode
+    %{
+        def GetItems(self):
+            return [item.Cast() for item in self.GetItemsDeque()]
+    %}
+}