Rename some classes in grid system.

Note: The naming of classes is still confusing. "cell" usually refers to class "Grid", and "grid" usually refers to class "NGrid". But it requires a lot of changes to clean this up.

src/server/game/Chat/Chat.cpp

@@ -1240,7 +1240,7 @@ GameObject* ChatHandler::GetObjectGlobalyWithGuidOrNearWithDbGuid(uint32 lowguid
     if (!obj && sObjectMgr->GetGOData(lowguid))                   // guid is DB guid of object
     {
         // search near player then
-        CellPair p(Trinity::ComputeCellPair(pl->GetPositionX(), pl->GetPositionY()));
+        CellCoord p(Trinity::ComputeCellCoord(pl->GetPositionX(), pl->GetPositionY()));
         Cell cell(p);
         cell.data.Part.reserved = ALL_DISTRICT;
 

src/server/game/Chat/Commands/Level3.cpp

@@ -3470,7 +3470,7 @@ bool ChatHandler::HandleRespawnCommand(const char* /*args*/)
         return true;
     }
 
-    CellPair p(Trinity::ComputeCellPair(pl->GetPositionX(), pl->GetPositionY()));
+    CellCoord p(Trinity::ComputeCellCoord(pl->GetPositionX(), pl->GetPositionY()));
     Cell cell(p);
     cell.data.Part.reserved = ALL_DISTRICT;
     cell.SetNoCreate();