SHA1 Payload-Digest should use base 32 and not base 16

[thomasegense]

I know that the Warc specification do allow base 16 (https://iipc.github.io/warc-specifications/specifications/warc-format/warc-1.1/#warc-payload-digest). But since most other Warc tools all produce base 32, SHA1, it would be beneficial for the community to use the same standard.

The following tools all produce base32:
Heritrix
wget
Webrecorder

It was discovered when the warc-indexer in the webarchive-discovery project (https://github.com/ukwa/webarchive-discovery/tree/master/warc-indexer) reported errors with the payload when indexing warc-files generated woth Brozzler.