Correctly check for array members to avoid "Warning: Illegal string offset 'h' in ...\lib\plugins\dw2pdf\mpdf\mpdf.php on line 9131".
Add two replacement patterns for including the page's namespace in PDFs:

@NS@      The standard namespace string with colons as separators, as
          returned by getNS($id).

@NS_CSS@  A modified version of the above, with colons replaced by two
          underscores, for safe use in CSS class names.
Merge branch 'mpdf-isset' into samwilson
Merge branch 'ns-replacement-patterns' into samwilson
Added new replacement pattern for Revision Number (@REVNUM@). #22
Start revision counting from 1.  Ref #22.
Merge branch 'issue-22' into samwilson