Add transformers to rename, filter, and transform object fields

[yaacovCR]

Fixes #819.

This pull request follows direction of approach suggested within that issue and within PR #964, but is more generic, allows for generic transformation, request and result wrapping on a per field basis.

• If this PR is a new feature, reference an issue where a consensus about the design was reached (not necessary for small changes)
• Make sure all of the significant new logic is covered by tests
• Rebase your changes on master so that they can be merged easily
• Make sure all tests and linter rules pass
• Update CHANGELOG.md with your change. Include a description of your change, link to PR (always) and issue (if applicable). Add your CHANGELOG entry under vNEXT. Do not create a new version number for your change yourself.

[yaacovCR]

I think similar to #1104 and other recent pull requests, the failing tests are extraneous to the changes here, and fixed by #1102.