Allow setting of PDF metadata

[rinorway]

According TCPDF documentation following metadata can be set.

$pdf->SetAuthor();
$pdf->SetTitle();
$pdf->SetSubject();
$pdf->SetKeywords();

It would be nice to be able to add those in the PDF template, so you can set eg the title to "Invoice nr {{invoicnr}} for {{clientname}}"

[emillod]

We did something like that. As far as i remember we've created pdf config file in Custom directory