Add AC and DC relay diagrams

My initial foray into Tikz was during Halloween
overnight. I got out of lectures, napped, and headed
to work overnight at Children's Hospital. I hoped for
a quiet night so that I could spend a little time on
experimenting with Tikz, but one of my patients ended
up being a Code Blue. The reduction of time meant that I
had to choose between messing around in Tikz or
knocking out the diagrams and finishing the lab report
after work.
I was dressed like a ninja that night.