cmd/audittrail: download and upload file

[adamdecaf]

What were you trying to do?
A command line utility for managing files inside the audit storage would be helpful. This allows us to manually add files that were uploaded manually. Also to download files and verify their contents.

# example, would have more CLI flags and options
$ go run ./cmd/audit help

  download <path> 
  upload [--org <string> <path>