Revision 169041

o Refactored RepositoryCleaner to use DiscoveryPhase and RewritePhase.
o Added the ability to read a pom and figure out whether it's a v4 pom (based on presence of modelVersion)
o Added a more accurate counter for artifacts that are actually rewritten successfully, rather than just the ones that enter the rewriting process.
o Probably need to add the phases still...