Implement remote ports forwarding support in pipe tunnel

[tcibinan]

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Resolves issue #2587.

The pull request brings support for remote ports forwarding in pipe tunnel. It allows to share a machine local ports with remote hosts without a direct network connectivity to the local machine.

Check the following code snippet to get an overview of how the implementation works.

# start receiving pipe tunnel remotely
pipe ssh pipeline-12345 pipe tunnel receive -ip 4568 -tp 4567

# start transmitting pipe tunnel locally
pipe tunnel transmit -th pipeline-12345 -tp 4567 -oh 127.0.0.1 -op 4568

# start some http application locally
nohup python2 -m SimpleHTTPServer 4568 &
nohup python3 -m http.server 4568 &

# make an http request remotely
pipe ssh pipeline-12345 curl localhost:4568

See pipe tunnel transmit --help and pipe tunnel receive --help outputs to find out more about the new functionality.