Updating AL_USDMaya to work with usd-0.19.1

[sirpalee]

Description (this won't be part of the changelog)

The following PR updates the plugin to work with the latest changes found on the dev branch. The changes won't build, because of UsdImagingGLEngine::TestIntersectionBatch was removed, without any alternative. For now, I left that piece of code unchanged.

Changelog

These entries will be used to update the changelog.

Use Markdown list syntax for each entry.

Filled out fields will be added to the changelog.

Added

Added support for 0.19.1 version of USD.

Changed

Deprecated

Removed

Removed support for 0.18.11 version of USD.

Fixed

Checklist (Please do not remove this line)

• Make sure the Title and Description of the PR make sense and provide sufficient context for your work
• Do any added files have the correct AL Apache Licence Header?
• Are there Doxygen comments in the headers?
• Are any new features, behaviour changes documented in the .md format documentation?
• Have you added, updated tests to cover new features and behaviour changes?
• Have you filled out at least one changelog entry?

[sirpalee]

Added a quick take on subclassing UsdImagingGLEngine as discussed in # 133. It's not tested, formatted or has its functions exported properly for now.

[sirpalee]

Updated formatting to match the rest of the codebase and ran some tests. Everything works as expected.

I'm not sure about the best place for "Engine", for now, I put it into the nodes subfolder since it's not really used anywhere else. Also, since it contains code copied directly from UsdImagingGL, should I add the Pixar copyright headers to Engine.cpp?

[murphyeoin]

@sirpalee thanks for all of your hard work here, we're a bit tardy on approvals at the moment (I'm going to blame Australian summer holidays), we're waiting to have our own 19.01 build working internally to allow us to test this..

[fabal]

Thanks @sirpalee , just two things:

• could you keep only changes related to this PR and remove other ones?
• would you mind changing the base branch from master to develop?
  Once done, we are now ready to merge your work.

[sirpalee]

@fabal Rebased! Now it should only contain changes that are required to make AL_USDMaya compatible with usd-0.19.1.

[fabal]

Awesome, thanks.

[pmolodo]

Cleaned up the commit history a bit and rebased, if you haven't already merged this...

[b0ssi]

Thanks @elrond79, we will be merging this shortly.