Better and more comprehensive npc descriptors

[ryceg]

npc.descriptor is a getter which takes a random string from the npc.descriptors array, which allows for easy writing. The setter npc.descriptorsAdd() runs data validation on the provided string, and trashes duplicate results. More descriptor types that respect adjectival precedence (a "lovely little old rectangular green whittling knife" is acceptable, but a "green rectangular old little lovely rectangular whittling knife" sounds terrible) would make for an immediate improvement upon the entire presentation.

Adding descriptors based on live events or other things would be an easy way to make the results less predictable and more personalised.