Delivery rework
Clean up destination code and add some functionality
- Split the destinations into separate files
- New DestinationTempFile for writing tempfiles into the destination which eventually get added
- All of the close() methods are now streaming
- Implemented ChecksumDecorator, so we get a SHA1SUMS file
- Implemented FetchFile decorator, so we get a rudimentary fetch-all.sh script
- Configured Docker and delivery for local development to have a separate volume mount for serving files