Replace World::getConfig with World::getFloatConfig, World::getIntConfig, and World::getBoolConfig.

Also fix a warning from a previous commit.

--HG--
branch : trunk

src/server/game/Instances/InstanceScript.h

@@ -176,7 +176,7 @@ class InstanceScript : public ZoneScript
         void DoRemoveAurasDueToSpellOnPlayers(uint32 spell);
 
         // Return wether server allow two side groups or not
-        bool ServerAllowsTwoSideGroups() { return sWorld.getConfig(CONFIG_ALLOW_TWO_SIDE_INTERACTION_GROUP); }
+        bool ServerAllowsTwoSideGroups() { return sWorld.getBoolConfig(CONFIG_ALLOW_TWO_SIDE_INTERACTION_GROUP); }
 
         virtual bool SetBossState(uint32 id, EncounterState state);
         EncounterState GetBossState(uint32 id) const { return id < bosses.size() ? bosses[id].state : TO_BE_DECIDED; }