Implement addTypename option and remove queryTransformer

[stubailo]

Fixes #616

TODO:

• 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
• Add your name and email to the AUTHORS file (optional)
• If this was a change that affects the external API, update the docs and post a link to the PR in the discussion

[glasser]

FYI: the jsdoc for the ApolloClient constructor still documents the unsupported queryTransformer rather than addTypename