PDF: Add page numbers #2401

It was suggested that we add Page numbers in the PDF reports, which are useful if users print out the report or discuss with their colleagues.

Not sure how hard it is to do this with the PDF lib but should be a quick fix?

I'd also include the report's date and (if available) period or something. I'll be fixing that in the next week.

Adding in the footer the "Date Range: X" shown on the front page would be great indeed. Maybe also adding the website name?

(In [4675]) fixes #2401.

EDIT: Sorry for PDF.php - seems like i hit the source-code beautifier in this file.

Changes were made in rows 18, 61 and 99-107. The other files should be correctly showing the changes.

pitcpdf: if we're extending a lib, the new class file should be in the Piwik namespace.

(In [4676]) fixes #2401 with Anthon's comment incorporated. (use Piwik Namespace when extending a lib)

(In [4677]) Refs #2401 Fixing build adding SVN keywords