Torrent file rewrite

Nobody has claimed this yet.

When https://github.com/internetarchive/dweb-transport/issues/22 and https://github.com/internetarchive/dweb-gateway/issues/33 are fixed we need to rewrite Torrent files, at ingestion and either on the fly, or via a batch process.

Code for rewriting on the fly is in [Archive.py](https://github.com/internetarchive/dweb-gateway/blob/master/python/Archive.py) that code will need trivially rewriting to use the URL format from https://github.com/internetarchive/dweb-gateway/issues/33 and the URL from https://github.com/internetarchive/dweb-transport/issues/22.

The code (or existing ingestion code) could be adapted for writing on ingestion, or for rewriting as a batch process.

Sam also suggested asking WebTorrent to try https & ws if tracker only supports http URLs since they are obviously unusable in webtorrent. https://github.com/internetarchive/dweb-transports/issues/5

Start by reading python/Archive.py and the linked dweb-transport and dweb-gateway issues, since this work depends on their fixes. Decide whether rewriting belongs at ingestion, on the fly, or in a batch process. Done means Torrent files use the URL format and URL specified by those issues; the WebTorrent HTTPS and WebSocket suggestion is a separate consideration.

Written by the indexing model from the issue text.