Refactor ExtraActions test class

Add: Rename the ExtraActions.recordArgument() method to storeArgument().
Fix: Resolve some small style issues in the ExtraActions class.
Fix return event system

Fix: The DefaultReturnEventExtensionRequester blocked all incoming ReturnEventExtensionWrappers, not only the return events. That caused the DefaultReturnEventExtensionReturner not to receive any request events.
Fix: The DefaultReturnEventExtensionReturner didn't handle ReturnEventExtensionWrappers. Instead, it just tried to handle plain events.
Small style fixes

Fix: Some more very small style issues.