Feature: Create a jsonschema and guide for processing system components

[yardasol]

Background and motivation

SaltProc's reprocessing capabilities are a core component of the application. Currently, there is little information on the theory and structure of the processing components file(s) in the online documentation

Description of idea

Add a jsonschema for the processing components file, as well as a Theory or User Guide section in the sphinx docs discussing both the JSON and graph components of SaltProc's reprocessing scheme.

Implementation details

n/a

Potential snags

It may be difficult to make the jsonschema