* Adding PDF plugin, based on the submission from jeremy lavaux and Lyzun Oleksandr.
 * I rewrote nearly all code to comply with Piwik coding styles/guidelines/ etc.  and also because it had to use the Metadata which wasn't yet created when the PDF code was initially written
 * Features customizable PDF reports (based on metadata reports), with description + scheduling (daily/weekly/monthly) and send to current user as well as additional emails listed 
 * Added helper function Piwik::getCurrentUserEmail()
 * Refactored window modal popover into a helper method piwikHelper.windowModal (used to ask confirmation when deleting stuff) Refs #1490
 * Refactored the Goals CSS into generic CSS which can be reused and is reused for PDF UI
Refs #1184
 * The callback must pass $this instead of the class name as it 
TODO
 * test scheduled tasks send email properly (email looks good + attachment works)
 * Add comment header in PDFReports files
 * Can we remove some files in TCPDF which adds a lot of space in the release (eg. some fonts in libs/fonts ?)
 * Test PDF with UTF8 characters


git-svn-id: http://dev.piwik.org/svn/trunk@2697 59fd770c-687e-43c8-a1e3-f5a4ff64c105