Supports setting WARC prefix for WARCs inside WACZ to `<org slug>-<slug
[crawl name | first seed host]>`.
- Prefix set via WARC_PREFIX env var, supported in browsertrix-crawler
1.0.0-beta.4 or higher
If crawl name is provided, uses crawl name, other hostname of first
seed. The name is 'sluggified', using lowercase alphanum characters
separated by dashes.
Ex: in an organization called `Default Org`, a crawl of
`https://specs.webrecorder.net/` and no name will have WARCs named:
`default-org-specs-webrecorder-net-....warc.gz`
If the crawl is given the name `SPECS`, the WARCs will be named
`default-org-specs-manual-....warc.gz`
Fixes#412 in a default way.