Modding improvements

The 'AI Considers advancing before firing' change seemed interesting, and trying to design a skills architecture was doing my head in.

I've removed the try...except thing from the Dispatcher, because my AI code was throwing type errors, and the try...except was doing my head in.
The existing code already considers accuracy, and I've put in a bunch of changes that allow the expected damage to be recalculated based on a hypothetical range (instead of the actual range).