Fixes to Rocket structs/traits with foreign implementations

[KinanBab]

• Rework FirebaseAuth token so it's secure, currently alohomora calls FromRequest on foreign code.
• BBoxResponder currently implemented for (BBox<T: Responder, P>, context), calls foreign responder implementation. Replace with a list of know types (e.g. strings, ints, etc).
• ResponseBBoxJson and RequestBBoxJson from 06839b1