Do not return pointers from getters. Do not pass pointers to the methods
that does not modify the checksum. Add `Empty` method.
Signed-off-by: Pavel Karpy <carpawell@nspcc.ru>
This is done to prevent import cycles when `object` package needs any other
that requires `object.ID` or `object.Address`.
Signed-off-by: Pavel Karpy <carpawell@nspcc.ru>
