Dfb

- Will now compress and upload snapshot files from incomplete runs (such as having errored, etc).
- Snapshots are now written to the cache dir instead of temp dir so that they persist across failed runs.
- Adds `--upload` to `advanced dbimport` to upload the import files to the repository
- Minor Bug Fixes:
- stats with no current transfers

These additions further hardens the snapshots as a *secondary* source of information. The files themselves remain ground-truth regardless!

- **Potentially Breaking**: Change the way dfb handles symlinks on local-to-local backups. See [symlink update document](symlink_update.md) for more details and how to convert the remote.
- **Important**: Setting `links` in the config is deprecated. Use the equivalent noted in symlink update document](symlink_update.md) in the `rclone_flags`.
- This better matches rclone's default behavior, fixes the prior issues with restore, and closes 1

- Added option to specify a directory (including an rclone remote) of files to import for `advanced dbimport`.
- Improved stats on transfer and fixed bug where would start at 0 after some time.
- Minor fixes and improvements.

Minor!

- Added `DFB_OVERRIDE_TIMESTAMP` and `DFB_OVERRIDE_UNIXTIME` environment to override the current time. These should be used carefully!
- Documentation

- Moved advanced config items into regular config
- Added minimum size to reference vs upload again
- Bug fixes and sanity checks on smart splitting.

- Snapshots are used to fill reference files. This is a MAJOR improvement if you have a lot of references since they all do not have to be read again
- snapshot output can be auto-compressed
- Bug Fixes