fix: schemas/VegCore/ERD/VegCore.ERD.mwb: project: allow it to have a dataset rather than being one, because projects do not always have separate attribution requirements (e.g. in Madidi they don't). this also fixes a bug where projects whose datasets had a parent dataset (e.g. VegBank) would need a dummy event for that parent dataset so that the fkeys on both dataset.parent->dataset and event.parent->event would be satisfied. added project__unique constraint on name within dataset.