Project management

We need to be able to store Documents in a folder/project/corpus for easier management. It is not clear yet what data should be stored there yet (to be shared between a corpus of documents), so some analysis is necessary.

I'd like to not have to differentiate technically between Project, Corpus and Collections, and have a two level structure (folder+document). Because i think most use cases can be solved with a search input (if metadatas are not enough to filter we can eventually add tagging). Also tree structures are often catastrophic performance wise and UI wise (select documents across the tree).