Add support for graphql

[vinistock]

It would be nice if Sail provided the appropriate types to be used by applications that have a GraphQL based backend. I'm not sure if defining the types inside the engine is enough or if any code would be required in the main app.

Some possibilities that can be explored:

1. Figure out a way of defining all that is needed from within the engine
2. Provide the types and add documentation on how to add them to the GraphQL endpoints so that developers know how to use it
3. Create a generator that will install Sail types in the main application