Scripts: Implemented virtual function DoCastSpellOnPlayers (self-explanatory) and CheckRequiredBosses checking states of other bosses before allowing combat with selected one

Scripts/Icecrown Citadel: Added checks to prevent skipping bosses

src/server/game/Instances/InstanceScript.h

@@ -173,6 +173,9 @@ class InstanceScript : public ZoneScript
         // Remove Auras due to Spell on all players in instance
         void DoRemoveAurasDueToSpellOnPlayers(uint32 spell);
 
+        // Cast spell on all players in instance
+        void DoCastSpellOnPlayers(uint32 spell);
+
         // Return wether server allow two side groups or not
         bool ServerAllowsTwoSideGroups() { return sWorld->getBoolConfig(CONFIG_ALLOW_TWO_SIDE_INTERACTION_GROUP); }
 
@@ -183,6 +186,10 @@ class InstanceScript : public ZoneScript
         // Achievement criteria additional requirements check
         // NOTE: not use this if same can be checked existed requirement types from AchievementCriteriaRequirementType
         virtual bool CheckAchievementCriteriaMeet(uint32 /*criteria_id*/, Player const* /*source*/, Unit const* /*target*/ = NULL, uint32 /*miscvalue1*/ = 0);
+
+        // Checks boss requirements (one boss required to kill other)
+        virtual bool CheckRequiredBosses(uint32 /*bossId*/, Player const* /*player*/ = NULL) const { return true; }
+
     protected:
         void SetBossNumber(uint32 number) { bosses.resize(number); }
         void LoadDoorData(const DoorData *data);