* deprecates awaitTermination, shutdown and isTerminated
* introduces a terminate-method that returns a Future[Unit]
* introduces a whenTerminated-method that returns a Future[Unit]
* simplifies the implementation by removing blocking constructs
* adds tests for terminate() and whenTerminated
* Added a setter for Java lambda actors to "hide" the not so nice looking type signature of the "receive" method.
* Updated docs to reflect the changes.
* Converted samples to use the new setter.
