Separate tool for generating model types and classes from the input schema

[dzhelezov]

The model types generated from the input schema are buried inside the warthog-based graphql-server files and are decorated with warthog annotations. This leads to the undesirable side-effect that the mappings are inevitable dependent upon warthog, and the processor is tightly coupled with the warthog-based graphql-server.

It would be desirable to have a separate tool with clean semantics, which would generate the necessary types and interfaces from the input schema + typeorm schema definitions