Retreiver - Delete cleanup

[MarkDaoust]

Description of the bug:

• Resource objects (Corpus, Document, Chunk) should have .delete methods
• Methods like document.delete_chunk(chunk.name) should work on chunk objects not just chunk names.
• Document and Chunk should probably have ".parent", or ".document" or ".corpus" methods.

Actual vs expected behavior:

No response

Any other information you'd like to share?

No response