Blender Git Loki

Hooked new iteration into existing writer creation

The writers still write the wrong data; calling them should be done
differently, and more should be done based on evaluated rather than
original data.

NULL -> nullptr

Working on a smarter way to construct the USD object hierarchy

This includes delayed writing to USD, which breaks things for now.

Removing some unused code

Start of abstract hierarchy iterator for exporters

Abstracted hierarchy walking of Alembic exporter

Reorganising USD code in a breaking way

Support instanced collections

Add some more timing & more useful temp logging

Just a quick hack getting USD support in there to export a mesh

Abstracted some code for moving towards collection instances

Reorganising the USD exporter to be more like the Alembic one

Removed unused includes