0.4.2

• Commands such as restore and ls that operate on a version, will by default operate on the last complete version, rather than defaulting to the last version altogether and then potentially complaining it's incomplete. Similarly for the SourceTree::open API when given no BandId argument.

• Some backup work is parallelized using Rayon, giving a mild speedup for large files. There is potential to much more work here, because backups are generally CPU-bound in Snap compression and BLAKE2 hashing, and Conserve should try to use every available core.

• Various internal rearrangements including treating stored and live trees as instances of a common trait, to enable future features.