Fixed some bugs, rebalanced craft costs and sell values, tweaked promotion.

explosions were not affecting items properly (unconscious / inventory)
promotion valued missions and kills equally, and ignored stats.
Promotion is now: stat_based_points + #missions ^ 0.5 * #total_kills
stat_based_points values a soldier's stats as follows:

FiringAcc	5 * value
Reactions	4 * value
Bravery		4 * value
TimeUnits	3 * value
PsiStr		3 * value
Stamina		2 * value
Health		2 * value
PsiSkill		value
Melee		value
Throwing		value
Strength		value