Rename property states to stateMachines in classTBSMParallelState.
Add exception regarding event registration and deferral.
Add event deferral definition to TBSMState.

Relates to issue #11
Merge branch 'develop' into feature/event_deferral
Add tests for event deferral in nested state machine configurations.
Updated documentation.
Merge branch 'feature/event_deferral' into develop