Unique Weapons

I just added unique weapons to my roguelike game engine. There are only a handful of them now. You never run into these weapons by just wandering the dungeon. You must defeat specific unique monsters. That causes the unique weapons to appear.

The explanation is that the some unique monsters carry unique weapons. They drop them when they die. The power of some of the uniques I got requires you to find and wield the unique weapons. Now that I got this done, I should be able to easily add unique armor.

I still need to do some testing on the unique weapon generation code. The unique monsters that carry the weapons occupy the lower levels of the dungeon. I have yet to implement any dungeon levels other than 1.

Looks like I know what feature I need to implement next. Then I test.