Core/GameObjects: Implemented gameobject_addon table, you can now set invisibility for gameobjects for quests

(cherry picked from commit 9d59d038f8b09ed036448e755cb0b102396a4ca1)

Conflicts:
	sql/updates/world/2015_04_05_07_world.sql
	src/server/game/Globals/ObjectMgr.cpp
	src/server/game/Globals/ObjectMgr.h

Core/GameObjects: fixed typo and logic (0 is a valid invisibility type)

(cherry picked from commit 23e8a3ce2928458649d94408d5deffb67339b1d6)

src/server/game/Entities/GameObject/GameObject.cpp

@@ -271,6 +271,16 @@ bool GameObject::Create(uint32 guidlow, uint32 name_id, Map* map, uint32 phaseMa
             SetGoAnimProgress(animprogress);
             break;
     }
+
+    if (GameObjectAddon const* addon = sObjectMgr->GetGameObjectAddon(guidlow))
+    {
+        if (addon->InvisibilityValue)
+        {
+            m_invisibility.AddFlag(addon->InvisibilityType);
+            m_invisibility.AddValue(addon->InvisibilityType, addon->InvisibilityValue);
+        }
+    }
+
     LastUsedScriptID = GetGOInfo()->ScriptId;
     AIM_Initialize();