unconnected systems preserve the order they were added
    when iterated for updating entities
component stores preserve order to prevent
    indeterministic results after iteration

entities can be checked for liveness

removed EntityCreationHandler
    notifying listeners is done in EntityManager
extended interface EntityListener to report
        on added / removed components

Entity.java: step method is no longer final

Entities can be loaded via EntityCreationManager and EntityFactory

added parameter interface for EntityFactory

fixed serialization issues

started versioning