Transport!YouAreFinished! - generalizing AbortSent flag

The transport is not in a usable state if either the abort request is sent or the transport was disposed. When in this state the transport should no longer be used. Before it was guarded by the AbortSent flag but the abort request does not necessarily have to be sent so the AbortSent was replaced with a new Finished flag which is set to true if either the Abort method was called or the transport was disposed.
Welcome?BackTransportAbortHandler - reverting TransportAbortHandler removal

We found that removing TransportAbortHandler caused a few issues and there might be more we did not find. Reverting change to avoid breaks.
Send ACKs to the connection waiting on the ACK not the acker itself

- These ACKs are used to verify that commands published to the
  bus have been received and processed (e.g. group commands).
- Previously, ACKs only succeeded if the waiter and acker were on
  the same machine and/or the acker happened to be the waiter.

#3037