Support running Tug Server as a service/daemon instead of just as console

[ebekker]

From #60 (comment) :

@theJasonHelmick pointed out that once Tug is started up it should return control of the ISE/powershell console to the user and continue running in the background.

We've only be supporting/testing Tug run in an interactive console, which is fine for development and testing, but for a production-worthy release we need install and run Tug as a true Windows Service or daemon.