create provenance command

One major problem around common SQL database is the issue of "provenance" whereby the who, why, when, what of the table changes is rarely clear or is stored out-of-band. Project:M36 has this information by design, so it should allow users to query how a specific tuple was added to the relvar or how a relvar was constructed- this could include the entire relvar history but also a summary.

Hypothetical:

```
:provenance s
| [commit hash | rvexpr | commit hash2 | rvexpr2]
```
Should we just expand the entire transaction graph relevant to the relvar?