Added a Motor Shield

Added an Arduino Motor Shield from RadioShack. Could have gone with the $8 one off eBay, but am somewhat leery of ordering from China. It would have taken two weeks to get here anyway. This little guy sets right on top of the Arduino Uno and lets you drive motors, steppers, servos, etc. from an external power supply - and I just happened to have a nice 12 volt one sitting on my shelf doing nothing.

Hmm... a model train is just a motor on wheels, and model train sets use lots of sensors and blinky lights, two other things that the Arduino is good at... I wonder...