Reads the .dwg file data of this object. 

Returns the filer status. 

This function is called by dwgIn() to allow the object to read its data. 

When overriding this function: 

1) Call assertWriteEnabled(). 2) Call the parent class's dwgInFields(pFiler). 3) If it returns eOK, continue; otherwise return whatever the parent's dwgInFields(pFiler) returned. 4) Call the OdDbDwgFiler(pFiler) methods to read each of the object's data items in the order they were written. 5) Return pFiler->filerStatus().