Reads the .dwg file data of this object. 

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().