Add support for auto-cloning

[mchitre]

Julia containers do not auto-clone messages. This means that the message sent from one agent to another can potentially be modified by the receiving agent, and the modification seen by sending and other receiving agents. This is the default behavior for the Java version too, as this is the performant mode. In this mode, received messages should be treated as immutable.

However, the Java version allows auto-cloning, which isolates different agents fully. Do we want to offer such an option on the Julia side too? To consider, and to implement, if deemed necessary.