Game server: implemented a zone flag for clan updates. Also, players also must now create a clan in their home zone only. Resolves #289 (I think?).
Game server/skill system: fixed a crash that occurred when single NPCs/mobs were targeted by buffs/debuffs. Problem is really #242, so the skill won't affect the mob/NPC still -- but it won't crash, either.
Game server/skill system: allowed for "Sacrifice" skill behaviour (as it is officially), so caster's HP is now taken (regardless of how much they have). We also now enforce that the skill be cast on someone else (specifics are handled by the skill type-specific code). Resolves #291.