Added loot database to game/data/loot.json.

This loot database allows us to place items into a map with this simple API:

theloot = {
  loot.make(1, 120, 126),
  loot.make(2, 121, 126),
  loot.make(3, 122, 126)
}
items.load(theloot)

This will place items with itemid in [1,2,3] on the map at the provided posx, posy.

The items come from game/data/loot.json.