[freeciv-ai] coreai: unit_desirability()

["Per I. Mathisen" <per@xxxxxxxxxxx>]

Did not use much (any) of Ross' code. Shuffled the existing code into a
more easily readable format and added and changed lots of stuff.

It now evaluates more unit abilities, and places less weight on some like
F_IGTER, which was way overvalued.

TODO: Add checks for ruleset hints (roles). But first someone with some
significantly more playing experience than me should check these hints for
validity.

Yours
Per

coreai3.diff
Description: Text document