Rebuilding Thunderspire Labyrinth, Duergar

I am probably not the only person that doesn't like beard-chucking duergar, so while working on updating Thunderspire Labyrinth I also decided to give them a new conic power to spare myself having to describe the original.

I wanted to avoid stepping on the toes of the tiefling. I figure if any of my players actually play one I'll let them take it instead of the quills, and also add in a duergar feat that lets them deal fire damage to nearby enemies after using a second wind.