The Urlset object should have to think about synchronization. It is the code
that uses the Urlset that shouldn't expect the Urlset to be thread-safe (just
like a HashSet isn't thread-safe. It make much more sense to not give all the
workers a reference to the same urlset object but all have their own

A seperate note is that I really think the worker should not extend from
Thread and a lot of the complex logic can be replaced by a simple executer service

(cherry picked from commit 031750fa)

* synchronize contains block to avoid duplicate entries

(cherry picked from commit 8213a63b)

CMS-9905: Update and align project pom parent and other dependency version references across all product projects

- old version x.y.z => (x+1).0.0
- bumped to latest project or release parent pom
- also updated copyright year where needed
- cleaned up/moved dependency version properties to main pom.xml from child pom(s)

HIPPLUG-1104: forward porting from 7.9: support prefix in parsing of property=condition. Also move code to MatcherUtils with unit tests

HSTTWO-3257 include hippo-cms7-commons because the parameter annotation classes move to the shared class loader

HIPPLUG-970: initial import of the sitemap standard plugin for CMS 7.10, cloned (unmodified) from the Forge sitemap plugin