WINDUP-253  Refactor WindupProcessor/Impl

Refactor WindupProcessor/Impl to simplify the API, move inner classes out and offload part of the code like prettyPrintRule() out of this important class.

    WINDUP-272 Refactor GraphContextFactoryImpl and GraphContextImpl
    WINDUP-253 Refactor WindupProcessor/Impl
    WINDUP-254 Improve error message in RuleSubset.