create provenance command

[agentm]

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> | [commit hash | rvexpr | commit hash2 | rvexpr2]

Should we just expand the entire transaction graph relevant to the relvar?