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.
At this point, let's not @Deprecate things, rather just perform the refactoring and update to the new code. We haven't released yet so no point to leave outdated code. Could you do this refactoring and update? Thanks!