Create Appropriate PrimitiveAssetAttributes from valid handle

[jturner65]

Motivation and Context

This small PR will take a valid PrimitiveAssetAttributes handle and use it to create and configure an appropriate PrimitiveAssetAttributes template. The handles of these templates encode all the relevant information required to properly instantiate a Magnum Primitive, and the handles cannot be changed by the user, so these handles can be expected to be valid descriptions/encodings of the described primitive template.

How Has This Been Tested

All c++ and python tests pass. C++ tests have been added to verify that template handles can be parsed into templates with appropriate field values.

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 great!