revamp - missing DQL GraphQL interop

[rderbier]

Explain the relation between GraphQL and DQL :

• the fact that Dgraph translates the GraphQL schema into a Dgraph schema
• the naming convention
• importing data for a GraphQL generated schema using RDF
• DQL in Lambda (pointing to the GraphQL doc maybe)
• the current limitation : deleting a mandatory predicate is possible leading to errors in GraphQL, corrupting the schema generated by the GraphQL deploy, etc ...