Data driven drugs

It might be fairer to call this a start at overhauling the iuse system, but the main difference at the moment is in drug handling.
I didn't switch everything over yet, but I need to get this off my plate and do some merging.  Further drug conversions are straightforward and can be done incrementally (as you can see in the commits that do so,  	7bf4220 and c2a98cd), also if people have feedback I'd like to hear it before converting everything first.