Save raw data when necessary

[nstepien]

When asagi fails to parse a post or an entire thread, asagi should save the raw html/json so that you could either fix the parser or fix the html/json manually, and reparse these when restarting asagi.
Same thing should happen when the DB is dead or busy.

[eksopl]

That's reasonable.

[nstepien]

I guess this is valid for files too, especially after the PDF fiasco.