Blender Git Loki

USD IO: attribute conversion improvements.

Initial implementation of logic to import USD
attibutes as Blender custom properites, with options
to import all custom attributes or only those
attibutes in the 'userProperties' namespace.

New export option to add custom properties to the
'userProperties' USD attribute namespace. This
option is enabled by default.

Removed hidden functionality where custom properties named
with the prefix 'USD_' were being saved to properties on the
USD prim that have the same name, without the prefix. This
code was not type safe and could lead to unexpected behavior
in case of accidental property name collisions.

Added support for converting between USD int, float and
double vectors and Blender array type custom properties.