Enhancement suggestion: new stayalive function

[ThePrez]

Proposal is for a new method in the AS400 class to set and enable a "stay alive" feature

Proposed method signature is:

public void setStayAlive(long milliseconds)

If milliseconds is greater than 0, then a request is sent at the specified milliseconds interval to all
currently opened connections to keep the connections alive. This is often needed to prevent
firewalls from dropping stale connections. If set to zero, then stayAlive will not be used.

To be in effect for a connection, this must be set before the connection is created.