Add getSkillIncrease() and setSkillIncrease() script functions to get and set the attribute bonuses received at the next level up as a result of skill increases.
Previously, getSkill() and setSkill() attempted to return and set the attribute bonuses, respectively. However, they mistakenly used a skill ID as a parameter for the attribute bonuses, when in fact npcStats.mSkillIncrease is an integer array of size 8 where the key stands for an attribute's ID. As a result, setSkill() had the unexpected side effect of messing up a player's major and minor skills because of the invalid values it was setting for npcStats.mSkillIncreases.