Statistics channel missing data, html usability

In ISC-Bugs 45340, I wrote:

The Statistics channel offers links to Zones and Traffic.
Both produce valid data, but display as blank pages with
a web browser.

Zones never had XSL (I provided the original
implementation, but punted on the XSL).

Traffic has XSL, but it wasn't updated to reflect the
split between IPv4 and IPv6 data. (This made the table invisible)

I've picked up enough XSL to fix my original omission,
and as penance for my sloth, fixed the Traffic bug as well.

This has not been acted on.

I've since added visiblity controls to the tables.

I'll create a merge request shortly.