New enemies, equipment, combat balancing

This patch adds a couple new medium level mobs, a unique off-hand equip, a new tribe gate feature, and a few balance changes. These new changes are being tested to improve weapon viability.

New mob: Vampire. Spawns as male or female (or sometimes as a bat). Ignores shield block, and does high damage if you are healthy but loses interest if you become unhealthy. Heals itself from the damage it does.