Fix to bug SWP12996: "Modified" flag was incorrectly set on Study object in 2 cases:
1) GetAttributeParameters() method always called FindOrCreateAttribute(), even when attribute was found and no creation was done. FindOrCreateAttribute always sets "Modified" flag on internal document.
2) Builder::FindAttribute() called _doc->Modify() which seems to be an error because no real modification to labels or attributes is done in this case.
