Feature/rest calls

- Apologies for the large PR, fixing the tests took some refactoring
- To make the demux executors non-blocking, I added some become/unbecome logic 
- Moved the request work to the executors and they will only pass the request up to parent if they are idle. Not sure if this is ideal
- Return response codes from the api endpoints

I was thinking that since this should only happen in the executors, and would mean different things for different executors it would make sense to keep them in a local protocol, to make the main protocol as small and transparent as possible.