Bumping version to 0.64.0
Merge branch 'release-0.64.0' into develop

* release-0.64.0:
  Bumping version to 0.64.0
Add denormalized structure builder

Useful for writing tests or manually creating structures.  It's
typically easier to hand write a denormalized model than it is to
write a normalized model, at least for simple cases (as is common
in tests).