Integrate our schema hacks into the parser

This extends the APIStar schema parser to add support for the official deprecated attribute on operations and parameters, our custom x-paginated attribute, and the dynamic editing of the base URL. This is the proper implementation of !55 (merged), !207 (merged) and !224 (merged).

Tinkering with the parser is letting me learn more about it and understand better what to clean up in #42.