* Separate variable service in its own module

* Counting entity changes

Moved to new Liquibase version and reverted the schema change + cleaned up slf4j-log4j dependency scope

Refactoring and tweaks of the async executor after some serious load testing on AWS. Introduction of a Spring-JMS message-based async executor (easily portable to other flavors of messaging), also tested on AWS with some very nice results :-). A blog will follow soon.