twisted.tap.portforward should use string endpoints for listen and destination addresses

[exarkun]

Currently the portforward options are somewhat confusing. There are three of them, two for ports and one for a host. After a little puzzling, it's possible to figure out that host and dest_port define a remote TCP server to forward connections to, while port is a strport description of an address to listen on.

The current naming scheme mixes local with remote making it harder to figure out how to use the tool. But it also limits the forward destination to TCP addresses. It would be great to use endpoints to allow any sort of remote address to be specified. As well, it would be good to update the use of strports to endpoints for the local listening address.

This would be an excellent, simple showcase of the features you get with endpoints.

[tpratt]

fix docstring, probably shouldn't t.python.deprecate in this case.

[thijs]

All new public methods, classes and modules need an @since: 11.0 marker.

[moshez]

It is better to put the -p/-h/-d ==> newer stuff code inside the option parsing (after "if selfconnect? is None") line: create selflisten? and selfconnect?. This way, when deleting old bw stuff, only one place needs to be touched.

Also, address thijs's comments :)