Switch to __dir__ entry point for introspection as Python 3 dropped support
for __members__/__methods__.  This is backwards compatible to Python 2.6.

Module initialization adjusted to complete type setup (needed for tp_dict)
via PyType_Ready.

Change-Id: Ie1f7b9dd4279242de89d009eb7acdc8c786dab8f
Reviewed-on: https://gerrit.libreoffice.org/5375Reviewed-by: Michael Stahl <mstahl@redhat.com>
Tested-by: Michael Stahl <mstahl@redhat.com>