Add queryTransformer back into apollo-client

[chillu]

This is a subtask of silverstripe/silverstripe-framework#6333

This is a task required to validate and implement the fragment registry approach.

The queryTransformer feature has been removed from apollo-client v0.5 (original code). I'm clarifying why that's the case, and hoping to get it back. We'd also need to change it to pass along the Document rather than OperationDefinition in applyTransformers, otherwise we can't determine the name of the operation.

Ideally we get feedback from the Apollo maintainers if they're open to reinstating the feature (or suggest an alternative). If that doesn't happen, we could push harder by opening a pull request adding back the feature.

[chillu]

The Apollo authors don't see this as a library feature - which is fair enough, we should really solve this outside of the library itself (on the HOC construction). Closing, and adding more notes on the parent ticket.