Builders can now customize room forage

[nessalin]

We've added code that allows builders to adjust what can be foraged from individual rooms and how likely it is to be foraged.  This will allow for updating areas based on changes in the game world without requiring code changes or modifying an entire zone.  Some parts of a mine might yield better results, clearing an area may change what can be foraged, different areas of a ruin may return different artifacts, and so on.