Server registration config

Ability to specify an optional timeout config for a Server binding to a port.  This is to prevent a Server from staying in a "binding" state indefinitely while the port is unavailable.  Instead, if it cannot bind, the Server actor is killed.  This required a few changes to the WorkerManager and Worker actors, mainly around who watches the Servers for death, and correctly unloads them from the IOSystem.

@DanSimon 
I replaced withServer with the waitForServer calls.  I guess if we want to keep the "withServer" function around, we could replace the "end" call with a call that just does a serverRef.shutdown().

We can't redo "end" just yet, because tht would impact a buncho tests which rely on that to shutdown the io system.  Thoughts?  I'm open to leaving this as or, or reinstating the "withServer" call