Add option to send a SIGINT to the process being wrapped

In some console applications, it is necessary that they be signaled to shut down correctly to give themselves time to flush buffers, write status messages, etc.  For most console apps that require this, the proper way to send this signal is with a SIGINT. On windows this is the CTRL C event.  This PR adds in the ability for winsw to send that signal to the console app for it to gracefully shut down.  

My inspiration and test bed for this PR is the jruby console application LogStash that we run as a windows service.