Create event distribution module between Observation Manager and the network

For XWiki instances clustering (several XWiki on the same db instance) the easiest way to have everything working really synchronized would be to make the events management system send events between different instances of XWiki. That way every code in the wiki caching generated data and already having to catch event locally to clean their cache could be synchronized the same way.

See http://dev.xwiki.org/xwiki/bin/view/Design/DistributedEvents