- revision_number is now implemented.  All updates to persisted n-cubes now create a new n-cube row, with a new revision number.
- n-cubes are no longer deleted, just marked as a deleted (negative revision_number)
- getCubes() type of APIs only fetch existing (non-negative revision number cubes)
- existing check APIs check for n-cube regardless of deleted or not
- coming soon  - APIs to allow getting list of deleted n-cubes, APIs to restore deleted n-cube, and API to fetch all revisions of an n-cube