Removes most instances of pb.SignedMessage (there's more to take out but they shouldn't hurt anyone as is).
There used to be places in psserver where a PieceID was hmac'd with the SatelliteID, which was gotten from a SignedMessage. This PR makes it so some functions access the SatelliteID from the Payer Bandwidth Allocation instead.
This requires passing a SatelliteID into psserver functions where they weren't before, so the following proto messages have been changed:
* PieceId - satellite_id field added
This is so the psserver.Piece function has access to the SatelliteID when it needs to get the namespaced pieceID.
This proto message should probably be renamed to PieceRequest, or a new PieceRequest message should be created so this isn't misnamed.
* PieceDelete - satellite_id field added
This is so the psserver.Delete function has access to the SatelliteID when receiving a request to Delete.
* fix audit stripe selector to work if last segment is smaller than stripe size
* fix audit bug related to indexing an incomplete list of nodes returned by overlay
The old paths.Path type is now replaced with the new storj.Path.
storj.Path is simply an alias to the built-in string type. As such it can be used just as any string, which simplifies a lot working with paths. No more conversions paths.New and path.String().
As an alias storj.Path does not define any methods. However, any functions applying to strings (like those from the strings package) gracefully apply to storj.Path too. In addition we have a few more functions defined:
storj.SplitPath
storj.JoinPaths
encryption.EncryptPath
encryption.DecryptPath
encryption.DerivePathKey
encryption.DeriveContentKey
All code in master is migrated to the new storj.Path type.
The Path example is also updated and is good for reference: /pkg/encryption/examples_test.go
This PR also resolve a nonce misuse issue in path encryption: https://storjlabs.atlassian.net/browse/V3-545
