Shield rebalance

Al shields had their resistances eliminated, except for the Orc Shield,
which retains -20% to holy. Reminder: armor is now directly effective,
so values of 1,2,3, etc are very powerful compared to the effective 0-1
they were before.

* Small Round Shield: +50 defense, 0 armor
* Gold Shield: -50 defense, 2 armor
* Knight's Shield: -150 defense, 4 armor
* Herald Shield: -150 defense, 2 armor, retains insignia bonuses
* Orc Shield: -200 defense, 2 armor, retains qor sp bonuses, -20% holy