Clean up the stats page

[devmount]

Is your feature request related to a problem? Please describe.
The stats page is a bit messy. Only some charts are grouped in tabs, only some have a heading.

Describe the solution you'd like
Group similar charts and use the tab navigation for every chart type. Tab titles are the chart title and a tooltip shows the tab description.

Describe alternatives you've considered
Moving charts to dedicated page sections with corresponding headings (like "General", "Contacts" etc) would also make the stats page more structured.

Additional context
This would also make it easier to integrate new charts into the stats page without blowing it up too much.