Adding NIR next trains support 

Hey Paddy :)  You know me from BLUG :)

So, this patch adds basic support for NIR.  It supports:

* Getting a list of stations by ID and/or name
* Getting a short list of the next trains going from a given station to another (by id or name). This includes waypoints/stops, as opposed to just final destinations.
* A simple "nir" command line tool is included, as a quick interface to this.

This is not (yet) integrated with the existing APIs, but does currently work if you access its API directly (I made it available at opentranslink.services.nir).

The code currently requires mechanize, but I'll update it to just use urllib or something soon, if that works OK (haven't tried it yet).