Sqlite database grows without bound

[joshaber]

Currently the sqlite database just keeps adding things. That's less than ideal. We should have some way of trimming it.

Some things:

• We could trim down to the most recent level attribute-value for all keys.
• But it's tricky to know that someone's not holding on to an old database.
• How does this interact with #3?

[joshaber]

This has been partially addressed by 4a50b1952ab17d4a8e9bbfa242ea2c032c6d8d92, but:

• The API isn't public yet.
• It hasn't been tested thoroughly.
• Trimming might be something users would want to customize. Trim only the oldest x entries, trim when it's bigger than x, etc.

[joshaber]

-trim: is now public and functionally complete as of https://github.com/joshaber/Freezer/commit/cd688e2b7640890f6bd6daf1d0fbd32485f80a35.

It'd be great to provide more customization in the future.

[joshaber]

It'd also be nice if -trim: could make some safety guarantees, i.e., no open databases.