Rework HttpControllers

[nexus4880]

I added the class BodyAwareHttpController<TRequest> which works just as the ItemEventController<TEvent> does just as @seionmoya and I discussed.

Instead of inheriting from HttpController for your route and getting the body from the context within RunAsync you can instead inherit from BodyAwareHttpController and use the generic to put your expected body type.

I have converted all existing usages of context.GetJsonAsync<T> to instead use BodyAwareHttpController<T>.

[seionmoya]

I like the work but not the type name.
I think HttpDataController would work better for me.
@TheSpartaPT @Lacyway suggestions?

[seionmoya]

Resolved by changing BodyAwareHttpController<TBody> to HttpController<TBody>