nieuws/replies: read contents from database

nieuws/replies: read contents from database

Replace file storage by a PostgreSQL table.  Resign to the additional
dependency for this kind of social feature since it's much more appropriate
(especially with upcoming extensions), and optional similar to external
comment services.

Identical results after importing existing files:

	ls melding/2*/*/*.html | perl -MFile::Slurp -lnE '
		my ($page, $meta) = m{(.*)/(.*)};
		my ($time, $author) = split /[:.]/, $meta;
		$time .= "00" while length($time) < 14;
		$time =~ s/^(\d{4})(\d{2})(\d{2})(\d{2})(\d{2})/$1-$2-$3 $4:$5:/g;
		my $html = read_file($_);
		chomp, s/\\\K/\\/g, s/\n/\\n/g, s/\t/\\t/g for $html;
		say join "\t", $page, $author, $time, $html;
	' | psql -c 'COPY comments (page, author, created, message) FROM STDIN'