Merge pull request #21 from ncsaba/wdb-wrapper

wdb wrapper
Merge pull request #22 from ncsaba/wdb-wrapper

Wdb wrapper
Merge pull request #23 from ncsaba/wdb-wrapper

Wdb wrapper
Merge pull request #24 from ncsaba/wdb-wrapper

added Extrude primitive wrapper
Merge pull request #25 from ncsaba/wdb-wrapper

Wdb wrapper
Merge pull request #26 from ncsaba/master

added brlcad._bindings.BRLCAD_VERSION; conditionally add HRT primitive;