Oh rats!

Doing a lot of work on the entity and item databases for this round.  The game starts with the dungeon populated mostly by rats, with an increasing number of kobolds as you go down.  Lots more items will spawn around the level, and kobolds have some decent drop loot.

• Rats infest the top levels of the dungeon.  Kobolds appear in increasing number as you go down.
• Rats are relatively weak, but they'll still nibble you to death if you're not careful!
• Kobolds have been un-nerfed.  They are now properly armed.
• Tweaked the stats a bit.  Also new enemies should be easier to make.
• When you pick up an item, you will get the item under your feet.
• Armor is now a thing!  I've tweaked the attack algorithm to account for armor AC and damage absorption.
• Every item in the game now has a level and rarity that is used to control loot spawning.  The highest level item can only be found at level 10 or lower.
• Fixed a bug in the particle renderer.  Using page flipping now, so it should be a bit smoother.
• Unarmed damage dice increased from 1d1 to 1d4.
• 50% chance that *every room* will have a prize!
• You only get 1 health potion for free.  Go find the rest yourself.
• Some performance improvements.