NEXUS-5472: Multiple things.

Changes:
* added handling for remote URL changed case (EventDispatcher)
* config enforced to not let user break it (WLConfig + imple)
* smaller refactorings to make things reusable for scrapers
* parent-o-matic got new method and dupes removed (local walker, pathMatcher impl)
* remote scrape strategy implement and honors noscrape flags
* nexus scraper implemented
* other fixes