Moves the metadata about coverages into the object store

- Adds new method to dataset management to deal with latest data (and
  changes).
- Updates ingestion and dataset management to use the object store for
  metedata, avoids loading a coverage at all cost for metadata.
- Updates visualization and data product mgmt to use new format.
- Test(s)

Part of [OOIION-1401](https://jira.oceanobservatories.org/tasks/browse/OOIION-1401)