Consider Trait/Inheritance implementation for FTW objects

[JackDunaway]

For example, a Request kindof inherits from JSON. But not really; it's more like "a Request has a JSON wire-level protocol, and it would be handy to use JSON functions to modify this part of the Request object".

When a Request is created, it currently must clumsily create the FTW-Reply-MsgControl structure as a field within the JSON.

This is suboptimal for at least a couple reasons:

• the object cannot be iterated with Keys without exposing this private framework field to the application layer
• it's inefficient/brittle, where it would be more desirable to make each a strongly-typed private field of the Request object
• it represents both the Request and the Reply, where fields must be consumed from the Request in order to not be repeated to the Reply (this is actually both good and bad)

Ideally, the Request object could use JSON functions directly, where it's implicit that those functions act upon the Reply object embedded within the Request.