Added back the GDS for the simple_por block, which needs to be kept

separate if the top level is assembled and GDS is written without
hierarchy checks (which will then miss needed hierarchy checks in
the simple_por cell).  It got lost from the repository because GDS
files were in ".gitignore", so this restriction was also removed.

Author: RTimothyEdwards

.gitignore

@@ -1,2 +1 @@
 /mgmt_core_wrapper/*
-gds/*.gds