Ai relationship

This changes the relationship between any s in terms of how they regard each other.

Dispositions:
 * Hate (D_HT): Considers the target an enemy and will attack.
 * Fear (D_FR): Avoids the target, possibly while attempting to attack.
 * Like (D_LI): Will not attack the target, and may do other things such as cover for it.
 * Neutral (D_NU): Will not attack but will mostly ignore the target.
 * Error (D_ER): Rarely, a problem can occur and result in this disposition. NPCs will probably behave similar to Neutral.