Just inspecting the attribute block is sufficient.

There was a lot of duplicated code, some changes in the templates allows
to share the two generators.

Avoid "preparation" of export/import commands which baked in values like
the node name which might be changed in subclasses.
- Remove the builtin conversion table in favor of a simple rule to
  convert a C type to a function name part.

Just pass the name as char const* to register_node_reader() and let the function construct the ident.

Templates are put in separate files now, making the main script more
generic in nature