add script to put refdes in fab layer

refdes2fab.py

@@ -0,0 +1,9 @@
+import pcbnew
+import sys
+
+board = pcbnew.LoadBoard(sys.argv[1])
+for fp in board.GetFootprints():
+  fp.Value().SetVisible(False)
+  fp.Reference().SetLayer(board.GetLayerID('F.Fab'))
+
+board.Save(sys.argv[1])