Add fail-safe and scalability functionality to the Drools (CEP) rules engine

The Drools Rule engine is currently not fail-safe and scalable which is a requirement for Cloud deployment.
Add a possibility to persist the state of the working memory after each state change (perhaps linked to the fireAllRules()?) and related to that the possibility to restore the state in case of a crash (fail-safe requirement).
This persistent state store can also be used to synchronize multiple engine instances (scalability requirement).
Of course this has major impact on the performance of the engine, but it is the only way to make the engine useful in a multi-tenant Cloud environment