0.0.33

Added

• A run can be staged: ekr stage begin copies the store at its head into a stage of its own and
  prints the stage id; --stage <id> or EKR_STAGE=<id> joins every verb that opens an existing
  store to that stage; ekr stage publish <id> --expect-head <revision> appends the stage's
  revisions to the store in one append group, or refuses by name and changes nothing; ekr stage abandon <id> drops the stage; ekr stage list lists a store's stages. After a publication or
  an abandonment the stage's tenant holds nothing. A retried publish returns the first one's
  result and appends nothing twice. Stages run on SQLite and PostgreSQL; the File provider
  refuses them. docs/cli.md lists the verbs and their refusals.
• A PostgreSQL store's inventory is read under one provider capture, so a stage can be begun from
  a PostgreSQL store. ekr migrate still refuses a PostgreSQL source.

Changed

• Every store opener refuses a tenant containing ekr.stage: as stage-tenant-reserved; that
  marker names stage tenants only.
• A stage publication is elected through a new retained format,
  ekr.publication-preparation/4. A store holding one is refused by earlier binaries as
  inventory-preparation-unreadable.
• The Eventlog crates move from 0.5.0 to 0.8.1. The File provider's appends and in-window reads
  no longer grow with the journal's size.