[Protocol] Implement generic response with dyn (#56)

* Implement generic response as enum

* First draft of implementing into_common()

* Make common response type generic

* Use macros and generics to reduce repetition

* [Games] Add dynamically dispatched CommonResponse trait

This adds two traits: "CommonResponse", and "CommonPlayer", when the
generic game query function returns a response it returns a pointer to
its original response type that implements "CommonResponse".

Both common traits require that "as_original()" be implemented, this
returns an enum containing a pointer to the original type.

Both traits have a concrete method "as_json()" that returns a struct
containing data fetched from all of its methods as. This struct
implements serde and can hence be serialized as required.

The traits require a few other methods be implemented, those being the
fields that are common across all types. All other methods have a
default None implementation so that each response type only needs to
implement methods for fields that it has.

* [Game] Implement common traits for JCMP2 response

* [Fmt] Run cargo fmt

* Fix doctest failing

* Run cargo fmt

src/protocols/valve/protocol.rs

@@ -19,7 +19,6 @@ use crate::{
             SteamApp,
         },
     },
-
     socket::{Socket, UdpSocket},
     utils::u8_lower_upper,
     GDError::{BadGame, Decompress, UnknownEnumCast},