Named pipes for closing the app

Having a go at #186, though the PR right now is incomplete. Biggest issue is that I haven't worked out how to confirm whether my setup.exe is using my local build of Squirrel or the one in `packages`, so I'm not sure if the code I put in uninstall actually runs. Otherwise, the code needs tidying up.

I've dropped this into a clone of [Shimmer.Samples](https://github.com/shiftkey/Shimmer.Samples) and so far can get it to compile, and tell it to close with a separate command line app ([source](https://gist.github.com/rzhw/7114c0da8f707d67d09f)).