Label tree export

[mzur]

The Geomar people suggested that is might be useful to tag specific label tree versions. This is similar to "releases" of GitHub repositories. The use case is, that a specific version of a label tree can be "cited" in a paper. Ideally this should have a DOI.

Thinking about this, a DOI for a label tree in BIIGLE would be hard to come by, as it should be guaranteed to be archived and persistently available. Maybe we could offer a special export of label tree versions to Pangaea and they take care of the archival? This is a similar idea to the "publication report" ( biigle/reports#39 ).

[mzur]

The tagging will be implemented with label tree versions which are described in #31 (second draft). We could offer a label tree export as a CSV for each version on top of that.

[mzur]

The label tree export should be similar to a CSV report. Maybe we can even implement this with the existing architecture of the biigle/reports module.

[mzur]

Rather than biigle/reports this can be better implemented with biigle/sync. This can be a new "PublicLabelTreeExport" which does not include sensitive user data. This would open up the possibility for a futute "PublicLabelTreeImport" where users can move their label trees themselves between BIIGLE instances.