Scripts/Instances: Complete rewrite of the boundary system.

- Migrate boundary logic to Maps/AreaBoundary instead of having it sit in InstanceScript (to possibly allow use for other purposes).
- Implement the first five boundary types in Maps/AreaBoundary.cpp.
- Add boundary checks to Creature's update logic
- Add boundary data for all Northrend raids
- Add boundary initialization structures and methods to InstanceScript
- Modify EnterEvadeMode signature. It now passes a value from the EvadeReason enum as parameter to allow special casing depending on evade reason
- Remove previous (weird) boundary code that had them linked to GO spawns

src/server/scripts/Pet/pet_priest.cpp

@@ -44,7 +44,7 @@ class npc_pet_pri_lightwell : public CreatureScript
                 DoCast(me, SPELL_PRIEST_LIGHTWELL_CHARGES, false);
             }
 
-            void EnterEvadeMode() override
+            void EnterEvadeMode(EvadeReason /*why*/) override
             {
                 if (!me->IsAlive())
                     return;