Code-generate functions and compile-time parameter validation for REST API

This module should be the easiest, since (Swagger 2.0) specs are available [1] [2].

TODO:

• How to handle differing capabilities under each domain?
• How to discover the list of supported Wikimedia endpoints?
• Write the prototypal function. Should the parameters be passed as a map (perhaps this gives "required" semantics if cast to a struct?), or a keyword list?