--MarkerSets assignment to objects, 'interface' class and bindings

[jturner65]

Motivation and Context

This PR expands on the Markersets support added in this PR to make interaction with Markersets easier.

• Introduces a set of classes (MarkerSets, MarkerSet, LinkMarkerSets ,LinkMarkerSubset) to map convenience functions to a MarkerSets Configuration hierarchy, including python bindings. These functions include querying, accessing and removing nested configurations as well as adding marker points to any marker subset.
• Adds Stage/Object/Articulated Object support for saving the markersets present from the initialization attributes used to create the object.
• Adds functionality to transform a list of points from ao/object local space to global, and vice versa.
• Adds saving of scale as a vector for all constructs (ao's, objects and stages) on their creation.

How Has This Been Tested

Locally c++ and python tests pass.

Types of changes

• Docs change / refactoring / dependency upgrade
• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have completed my CLA (see CONTRIBUTING)
• I have added tests to cover my changes.
• All new and existing tests passed.

[aclegg3]

Looks good overall. Some nits and questions.
Mostly docstring typos.

[aclegg3]

Addressed my comments. Thanks!