Datasette-clone

- `-v` option now shows a progress bar during each database file download. 5
- Databases are now streamed to disk as they are fetched, rather than being stored in RAM

* Include `metadata.json` in `-v` verbose output.

* Download a copy of `metadata.json` to accompany the downloaded database files. 3
* Now has unit tests. 4

* `datasette-clone latest.datasette.io` now works - it assumes `https://` if protocol is missing. 2

* Added `-v` option for verbose output

* Initial working version