ignore self-redirect entries in lookupUrl:

[ikreymer]

• don't skip loading self-redirect WARC records so that http headers are still loaded
• add isSelfRedirect() check in lookupUrl to ignore self-redirect matches
• in case of self-redirect for specific timestamp, allow loading from later timestamp (by 10 seconds) to find a non-self-redirect
• fixes #130

[matteocargnelutti]

@ikreymer Tested locally in replayweb.page: I can confirm that it works 👏