Python Support for cross language APIView reviews

[mikekistler]

Language parsers need to include a language independent common ID for each classes, APIs and other entities so APIView can map them across the languages

In support of #4033

[tjprescott]

This is already done for Python.

[mikekistler]

@tjprescott Can you explain what was done in Python, so we can use this as the design for what to do in the other languages?

[tjprescott]

This was the implementation PR. It may need to be updated since it was never used:
77c0f52

Basically it looks for a file in the WHL or source called apiview_mapping.json which would map all of the local Python definition IDs to the cross-language definition.