FinalityHandler is insecure in that it is open to receive any transaction from any party.
Any CorDapp targeting platform version 4 or above is required use the new c'tors which take in FlowSession objects to the counterpart flow. This flow must subcall ReceiveFinalityFlow to receive and record the finalised transaction.
Old CorDapps (with target platform version < 4) will continue to work as previously. However if there are no old CorDapps loaded then the node will disable FinalityHandler.
* Consistent separation of Java and Kotlin sources via package names only
* Renamed the Kotlin tutorial files to match the class names
* Added Java example of LaunchSpaceshipFlow
