Game server: upgrade previews now show the item after upgrade; resolves #302.
Game server: upgrade previews should always succeed.
Game server/skill system: type 4 code now allows for spawns, although it still does not update the AI server. Refs #242.
Game server/skill system: type 1 skills now take AddDamage (additional damage) into account.
Game server/skill system: minor amendment to previous commit; if the target is a mob, we need to be using the absolute amount. Damage reduction only applies to players.