[node] Simplify the file structure of the Node

[snario]

Today the Node still has some amount of technical debt from the original creation of the library to support the Playground release and the integration of the machine which is now a subfolder inside of the package.

This issue is to evaluate the folder structure as a whole and make some improvements that make a material impact on the overall simplicity, code-reuse, and readability of the package.

Some potential improvements:

• Remove the implicit naming convention of operation.ts in favour of something that more clearly differentiates the request handler "receiver" from the implementation.
• Split out files in the machine subfolder into more logical containers if they can be or are already re-used inside the rest of the package

[cf19drofxots]

Waiting on jsonapi-ts to be merged in first (as that has updated the structure a bit with the resources / processors / etc)