Observable.subscribe().unsubscribe() dance to free up the MQ resources server-side.
* remove an unused import
* implement a FlowHandle<Transaction>.finalize method
* Rename finalize() to discard() - remove the collection and run discard individually
* Remove unused imports
* Observable.notUsed helper function
* Tweaks to comments
* FlowHandle implements AutoClosable
* Resolving conflicts and move notUsed to RPC module
* Copy Observable.notUsed in core module.
* delete discard method
* CORDA-305: Refactor CordaRPCClient into :client:rpc module
* CORDA-305: Remove the Kotlin test framework from the artifacts.
* CORDA-305: Migrate serialisation whitelist into node-api module.
* CORDA-305: Clean up unused RPC observables.
* CORDA-305: Add :client:rpc module to documentation tasks.
* CORDA-305: Include :finance into :client:rpc for its serialisable classes.
* CORDA-305: Move test classes into the correct directory.
* CORDA-305: Migrate :finance dependency from :client:rpc into DemoBench.
* CORDA-305: Update wording of TODO about handling Observables.