Added IP Connection

@gerritv Thanks for making Grbl-Panel. Here's my unsophisticated attempt at adding a feature, if you have any suggestions for improvement, please let me know.  Programming is a seldom used hobby of mine, I'm by no means an expert.

Added the option to connect to an IP address and port for those who have
added a WiFi option to their CNC machine, e.g. with a WiFly, as here:
http://www.shapeoko.com/blog/archives/1272