Preserve metadata between crate's source and destination

Currently, I don't believe that any metadata is copied from source to destination. We make forklift smart enough to copy the metadata over. Something similar to this may work:

source_md = md.Metadata(crate.source)
dest_md = md.Metadata(crate.destination)
dest_md.copy(source_md)
dest_md.save()

[ ] Should this be done only on destination creation or every time that the data is updated?

agrc / forklift

Preserve metadata between crate's source and destination #347