Added params onBefore/AfterTransition events

**NOTE**: Breaking change for extended classes of the `AStateMachine`, due to change of `AStateMachine::transition()` signature.

Added `$params` attribute on the `AStateMachine::transition()` method.
Params are passed as event params to the `AStateTransition` event objects raised in `AStateMachine::onBeforeTransition()` and `AStateMachine::onAfterTransition()`.