Recolor all book icons systematically

The book colors got a bit messy lately. This PR changes the color of books systematically.

Color key:
* Light red: martial arts
* Light green: crafting recipes (primarily)
* Magenta: teaches skill up to 1
* Brown: teaches skill up to 2
* Green: teaches skill up to 3-5
* Cyan: teaches skill up to 6-7
* Blue: teaches skill up to 8 or more
* Pink: just (!) for fun, morale +1
* Light blue: just for fun, morale +2
* Light cyan: just for fun, morale +3
* White: just for fun, morale +4 or more
* Dark gray: book with special use case which doesn’t fit into any category above.
* Light gray: Waste book. No skills, martial arts, crafting recipes, morale boost or special use case. Basically trash.
* Yellow: intentionally unused (used for sounds)
* Dark red: intentionally unused (used for IR)