Make RuntimeManager api working without persistence

UserGuide suggest using RuntimeManager instead of KieHelper/KieBase API due to many reasons (kie sesison strategies etc.)

API suggest that it can work without persistence:

RuntimeEnvironmentBuilder.Factory.get()
            .newDefaultInMemoryBuilder()
            .persistence(false)

bun when tried it leads to:
http://stackoverflow.com/questions/28365533/how-to-disable-jbpm-persistance

so recommendation is to go to KieHelper/KieBase approach again.

(I believe the KnowledgeBuilderImpl approach is even better because provides you a way to add processes to KieBase in runtime.. a subject to a different JBPM-4416)

Please either:

• remove persistence() and .newDefaultInMemoryBuilder support in RuntimeManager (as it doesn't make sense)

or

• create RuntimeManager without TaskService in this case, document that in RuntimeManager javadoc and user guide

• provide TaskService implementation working in memory

Preferable 3) or 2)