CONTRIB-4089 - Changed usage of TCPDF to PDF

The PDF class extends the TCPDF class, so the same functionality is accessible.
Fixed issue with defaults not being set when adding a new certificate
Increased version number
CONTRIB-4089 - Fixed location TCPDF folder was generated for Moodle versions 2.2 onwards
Increased version number
CONTRIB-4227 - Removed ampersands to prevent strict standards warning corrupting reports when in debugging mode
Fixed the position of the first and lastname when exporting a .txt file.
CONTRIB-4237 - Fixed the usages of the CERT_PER_PAGE and CERT_MAX_PER_PAGE
Added option to print 'grade category' grade
Merge branch 'master' of git://github.com/markn86/moodle-mod_certificate