open express.d.ts interfaces

- provides open interfaces for Request, Response, Application
- express's interfaces remain the same, but extend the open ones
amend passport.d.ts

- passport.d.ts has been amended to merge its Request extensions into
express's Request interface.
- removed now-unnecessary type coercions from passport-test.ts
Merge pull request #1994 from yortus/open-express.d.ts-interfaces

Open express.d.ts interfaces