Dfb

- Handles the situation when using `compare = 'hash'` but the checksum/hash is still missing, as can happen with some remotes. Falls back to `'size'` compare similar to rclone's behavior.
- Settable with `error_on_missing_hash` config
- More robust hash database even around missing hashes (unlikely to actually happen for the kind of remotes you would want to use a database but this should handle it.)
- Fixed bug with `reuse_hashes='size'` still caring about `mtime`

- Added the option to track moves and use a [server-side] copy instead of a reference. This only makes sense when the remote support server-side copy (not verified by dfb). It enables a cleaner representation without using bandwidth
- Tests for new capability

- Fixed removed feature.

- Adds the `disable_prune` (default to False) configuration option so that it is harder to accidentally prune. Makes it effectively append-only unless very, very explicit.
- Minor documentation updates

- Can specify `--deleted` (or `--del`) twice for `ls` and `snaphot` to *only* include deleted items

- Adds version count to `ls -ll`