Core/Player: Allow graveyards to be specified for areas, not only zones

Closes #14089
Closes #18006

sql/updates/world/6.x/2016_09_27_00_world.sql

@@ -0,0 +1,3 @@
+-- Changing subzone 6170 (Northshire, Elwynn). Was zone 12 before, not right.
+-- Part of my total fix for graveyard problems (https://github.com/TrinityCore/TrinityCore/issues/14089)
+UPDATE `graveyard_zone` SET `GhostZone`= 6170 WHERE `ID`= 105 AND `Faction`= 469;

src/server/game/Globals/ObjectMgr.cpp

@@ -5997,12 +5997,6 @@ void ObjectMgr::LoadGraveyardZones()
             continue;
         }
 
-        if (areaEntry->ParentAreaID != 0)
-        {
-            TC_LOG_ERROR("sql.sql", "Table `graveyard_zone` has a record for SubZone (ID: %u) instead of zone, skipped.", zoneId);
-            continue;
-        }
-
         if (team != 0 && team != HORDE && team != ALLIANCE)
         {
             TC_LOG_ERROR("sql.sql", "Table `graveyard_zone` has a record for non player faction (%u), skipped.", team);