Upload discovery

Choose the folder that contains your collection folders. The first folder level is the collection, the second is the subset (custodian); anything deeper is kept as the file's path. Each file is hashed here before it is sent, so what lands is provably what you had. Large files upload in resumable parts. A dropped connection re-sends one part, not the whole file. Very large productions still belong on the CLI; this is for the batches a browser can carry.