Always add warcinfo records to all WARCs

[ikreymer]

Fixes #553

Includes warcinfo records at the beginning of new WARCs, as well as the combined WARC. Makes the warcinfo record also WARC/1.1 to match the rest of the WARC records.

[ikreymer]

As discussed, one thing we may want to add is additional data to the warcinfo records, perhaps:

screenshots: type: screenshot text: type: text info (for QA crawls): type: pageinfo regular warcs + combined warc: type: combined or type: web?

[tw4l]

regular warcs + combined warc: type: combined or type: web?

+1 for web as best term we've come up with so far for general WARC records capturing web traffic

[ikreymer]

Will create separate issue / PR for additional type field