#142 Unable to get link to remote from Port.replication

[Ken Webb]

It's currently possible to get a remote link by called IPort.getLink(index). This is called on the port that owns the replications. But it's currently not possible to get the remote link from one of the replications instances itself, other than by directly calling getNextSibling(). But this is an implementation detail that should be hidden.

Add the following method to IPort/Port:
public IXholon getLink()
with no parameters.