Fix activiti 6 UI not working on some languages (see https://forums.activiti.org/content/activiti-6-ui-internationalisation-problem)

Implement ClassDelegateFactory and DefaultClassDelegateFactory, and use them in the DefaultActivityBehaviorFactory and the DefaultListenerFactory.

Added accessor methods to ProcessDefinitionQueryImpl and DeploymentQueryImpl.

ACT-4079 (NullPointerException in DbSqlSessionFactory.isBulkInsertable() when Custom Entity is inserted) : fixing Oracle, the old 'get()' needs to be back, but now _after_ the containsKey

Activiti6 Modify ClassDelegate to so that the way it instantiates classes can be overridden.

Rename ClassDelegate.instantiateDelegate to ClassDelegate.defaultInstantiateDelegate for external class, and added a non-static method for internal calls.

Fix multitenant mail server configuration

Only create default history manager if no other is set already

Multitenant process engine configuration with isolated schema for each tenant (with dynamic tenant registration).
+ Two implementations of multi tenant (isolated schema) async executors: one with an executor/tenant, the other one with a shared executor service but separate acquisition threads