Build system: Added option in vfx_platform_builder script to disable
requirement for Houdini or Katana plugins.
Katana: Handle USD purposes in KatanaPlugin.
"guide" and "proxy" are viewed in the viewport but not in renderer.
"render" is viewed everywhere (viewport and render).
Katana: Handle USD Lights.
All lights are scanned and put into a lightList at /root/world in Katana
to ensure the renderer find them. Since UsdLuxLight is not a concrete schema,
we made an ArnoldLight that inherits from UsdLuxLight and allow us to have generic
ArnoldLight into USD scene.
Maya: Variants support in the Walter outliner.
Arnold: primvar support for Usd PointInstancer
Bug fixes
Arnold: Texture coords stretching issue resolved.
Katana: crash when scene graph is evaluated and layers are changed.
Build system: The 'debug' flag is now propagated to every dependencies
Removed
Arnold: Version 4 is not supported anymore.
MtoA Extension: jsoncpp dependency not needed anymore.