monster and item parsing

We use YAML to parse in monsters and items.

Later, we will add races, skill/spell trees, etc. All these things
should be part of game assets, and loaded in upon game startup.
configuration file import

We now pass a single configuration file from which we load all of our
game assets.
Player: add Eq and Show instances
import item and monster databases
system of using affixes for items

Also, we use our own format instead of JSON/YAML for importing external
data; this gives us more fine-grained control, especially for error
messages.
framework for random item generation
improved affix parsing and item generation

Also, we now have the notion of item ratings, useful for item generation
and also in-game shops/merchants.