Skill comprehension/XP gain mechanics change

As I've mentioned elsewhere, skill comprehension > 100% didn't do a whole lot in the existing codebase. Even when skill comprehension did come into play, it just affected the likelihood that XP would get moved from the pool into the skill, which IMO is not more than a minor perk (despite there being a 3-point trait that boosts skill comprehension).

I spent some time playing around with this, and I propose that we remove skill comprehension and replace it with a boost to how quickly the XP pool fills. With moderate intelligence and Fast Learner, you get a nice but not absurd boost to XP gain, meaning you don't have to wait around as much to train your skills. With high intelligence and Fast Learner, you do get an absurd amount of XP - but you still have to actually go out and practice, which can be dangerous.

And there's the key bit: even though increased XP makes the game easier in a way, you still have to go out into the world in order to spend the XP. So, I find that it removes some of the tedium and waiting, but doesn't remove very much challenge, nor does it make you learn hard-to-train skills any faster (assuming that you're careful to always have XP before practicing that skill). In fact, I find that it can sometimes cause a change of player behavior that *increases* challenge, because I end up doing stupid things in order to spend ALL of my XP.