web: don't use wai-handler-launch with yesod devel
web: also launch a browser at startup; auto-terminate after 2m or on enter
We're now using the wai-handler-launch middleware. This injects a
script in each page that pings the server repeatedly, and terminates
the server if it gets no pings (ie there are no browser tabs
displaying the app) for two minutes. The server can also be easily
terminated at the console by pressing enter, yesod devel style.