Add CHANGELOG.md
Refactor WorkflowDispatcher: extract congestion control/monitor to top level class
Refactor WorkflowDispatcher: provide congestion control to dispatcher in constructor
Refactor WorkflowDispatcher: remove unnecessary mutex from CongestionControl API method (will be taken in Monitor)
Refactor CongestionControl: make wait naming consistent with its semantics (better naming would be nice)
Use LinkedHashMap -> deterministic iteration order
Remove unneeded static modifier.

Classes nested inside interface are automatically public and static.
Improve WorkflowExecutorListener javadoc.
Add test case queryWorkflowInstanceWithMinimalConditions
Improve unit tests in RepositoryServiceTest
Refactor RepositoryDao: use trimToNull
Remove unreachable code in ListWorkflowDefinitionConverter

Assertions in AbstractWorkflowDefinition guarantee that errorState always exists.
Improve unit tests in CreateWorkflowConverterTest and ListWorkflowInstanceConverterTest
Change HashSet -> LinkedHashSet: deterministic iteration order.
Add NflowJacksonObjectMapperTest
Add unit test check initialization without non spring WorkflowDefinitions.
Suppress unread public field warnings
Suppress unneeded casting warnings.
Refactor fields to inner class where they are used
Refactor CongestionControl
- make Monitor static as it does not access outer class state
- suppress naked notify warnings in callback methods