[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/gamespy/mod.rs

@@ -16,11 +16,18 @@ pub enum GameSpyVersion {
     Three,
 }
 
-/// Enum of versions and their ExtraResponse data
-#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+/// Versioned response type
 #[derive(Debug, Clone, PartialEq)]
-pub enum VersionedExtraResponse {
-    One(one::ExtraResponse),
-    Two(two::ExtraResponse),
-    Three(three::ExtraResponse),
+pub enum VersionedResponse<'a> {
+    One(&'a one::Response),
+    Two(&'a two::Response),
+    Three(&'a three::Response),
+}
+
+/// Versioned player type
+#[derive(Debug, Clone, PartialEq)]
+pub enum VersionedPlayer<'a> {
+    One(&'a one::Player),
+    Two(&'a two::Player),
+    Three(&'a three::Player),
 }