[GraphQL] Additional configuration options for schema generation

[lukasluecke]

It would be great to have configuration options for the following features:

• Use Relay-style pagination (edges, nodes, etc.)
• Generate clientMutationId

Could also be extended for future features (e.g. additional pagination styles, schema conventions, ..)

[alanpoulain]

Why not having some options to configure the schema, but I'm not sure about the ones you quote.
Having Relay-style pagination is a must-have IMO. And clientMutationId is not mandatory so I think it's OK to have it by default.