Adding tests for digest creation, and slightly refactoring FileStoreImpl.
Adding IDs to version metadata.
Making versions a SortedSet.

Less computationally efficient, but properly sorted now.
Updating version service to provide versions primarily by UUID, not name.
Adding SHA512 hash to JSON and as an ETag.
Returning 304 when downloading with If-None-Match and If-Modified-Since.
Adding private caching for downloaded files.
Using IS08601 with timezone in JSON output.
Renaming "version" to "versions" for consistency.
Removing FileInfo, and replacing it with a version list.
Selecting versions on ID rather than name.