Implement Piwik UI tracking for demo.piwik.org, using Piwik #2460

It would be nice to know, on the Piwik demo, exactly how users use the demo, what sections are most looked at, what parts of the datatables users click, etc.

We could therefore "plug" the Piwik Tracking "event" via trackPageView() on each click on a UI element: menu, submenu, Next/previous, Column sort, etc. and track these with a "pretty name" for the Pages> Page Titles report.

This would help understand what sections of the demo are more popular and how the demo is used. Also, this could be a featured use case of using trackPageView() to do an "event like" tracking!

#4589