- implement "random encounters" by simply populating the
  worldmap randomly by region.
- allow treasurelists to silently forward-reference archetypes
  (should have an extra checkign path for never-defined archetypes)
- fix GT_ENVIRONMENT, which had the semantics of putting treasure
  items _and_ their inventory on the floor, now only puts the
  items themselves on the floor.
- remove warning about generated inventory - some items simply
  can come with an empty inventory.
- do some other minor improvements.