Core changes:
- `object.ID` moved to new package `oid`;
- `object.Address` moved to new package `address`;
- `pool.Object` interface changes.
Additionally:
- Set container owner in `Agent.IssueSecret`.
- Remove no longer needed fields from `GetObjectParams`
- `Length` and `Offset` are never assigned. These values
are set in `Range` field.
Signed-off-by: Leonard Lyubich <leonard@nspcc.ru>
