We want to use those fields in the bucket-level Pointer objects as
bucket defaults, but we need to be able to get at them first.
I don't see any strong reason not to make these available, except
that it was kind of a pain.
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
* Clean up last segment handling
* Fix increment for AES-GCM nonce
* Fix stream size calculation
* Adapt stream store tests
* Fix Delete method
* Rename info callback to segmentInfo
* Clearer calculation for offset in Nonce.AESGCMNonce()
* Adapt to the new little-endian nonce increment
