Bundle format and functionality

An upload "bundle" is a data artifact that contains everything necessary to interpret the data of a single upload.

I needs to contain:

• raw files (optionally)
• archive (optionally based on a required)
• all upload and entry metadata
• all related DOI records
• all necessary schema
• a directory of all external references
• hashes/checksums, etc. ideally following some long-term archive standard

We should use these "bundles":

• to internally store immutable/published uploads
• transfer uploads from installation to installation
• import/export functionality