Fixed issue 06845: PDF statistics don't get pdfdefaultfont and pdffontsize
Dev: just getconfig for pdfdefaultfont and pdffontsize
Dev: Add an 'auto' to set default font for pdf like graph.
Dev: TODO : test inclded PDF font for specific language, and set default config to auto
Dev: Is set to auto, pdf size don't include font file, maybe lighter pdf file
Dev: Conflicts: application/helpers/admin/statistics_helper.php