Allow groups to specify which BioProject we upload their sequences into

[anna-parker]

By default we should still create a bioproject for each (group, organism), but we should also let users give a bioproject accession that we can upload sequences to.

At the moment we can hack this with one transaction in the ena DB. In future we should add this as a field when users upload sequences for a specific organism and they should be able to see it on their group page. We will also need to be able to update this in the deposition pod.