Simplify overly complex project internals

I have spent quite a lot of time working on this project. I was hesitant to create this issue because I felt like I am lacking a lot of know-how to propose such a significant change. However....

• version 1.5 introduced protobuf
• version 1.5 introduced websocket as transport
• version 1.5 abstracted RPC mechanics (request / response / response stream) as an unbelievably super generic abstract thing

I think it is apparent which part of the framework I consider in need of rewrite :). The generics in framework-rpc module makes working with the project so so so so so so much harder (both in terms of understanding what is going on and in terms of source code littered with unnecessary generic parameters).

I am creating this issue to start discussion (or maybe direct efforts) on how to rewrite this part of the project.

Start by reviewing the framework-rpc module and the changes introduced with protobuf, websocket transport, and the generic RPC abstractions. Trace how request, response, and response-stream mechanics are represented. Done would require an agreed rewrite plan, since this issue currently opens a discussion rather than defining a specific implementation or test target.