We were using mixed types for nonce fields. Protobuf
have storj.Nonce, metabase have []byte. This change
is a refactoring to have everywere its possible only
storj.Nonce.
Change-Id: Id54bd8481f30c721cdaf3df79206d25e7cfdab55
We were manually converting ObjectKey fields to []byte to use it with
SQL query but we can just implement Value method to convert it automatically.
Change-Id: I6d346f4b59718e1e8ef37cd9f95e613b864b42cd