Feature request: Header matching for db_tests

[iasdeoupxe]

While implementing #621 i have noticed that the "Match 1" calls seems to only evaluate the HTML body and doesn't allow to match against some parts within the header.

Just adding a "200" for that check might give false positives and it would be great to match against some header content like e.g. the following in the db_tests:

Content-Disposition: attachment; filename=RV130W_syslog.txt