Add pinhole materials to default materials

This adds the pinhole materials from `hexrd.resources.pinhole_materials.h5` to
the default materials list. They were copied directly from that file.

The materials added were: Mo, Pt, Ta, U6Nb, W

This is necessary for doing things like creating overlays for pinhole
materials.

Signed-off-by: Patrick Avery <[email protected]>

Author: psavery