Feature request: change "Purification and Healing" prayer book.

[bron]

I admit this request is largely prompted by my recent anguish in looking for copies of PB4 in an ironman game. But I think it is still legitimate:

The prayer book "Purifications and Healings" contains both of the two healing prayers that I never use: Cure Serious and Cure Mortal. If I have the time to waste, I'll instead cast Cure Light Wounds which has better cure/mana value. And if I don't have spare time, I'll use Heal. I would think the special books should have good prayers in them, not this junk.

I propose that Cure Serious and Cure Mortal be replaced by Cure Light and Heal in the Purifications prayer book. To compensate for the book being invulnerable, the Heal spell
should cost roughly double what it does in PB4.