Add a config option to enable the public body statistics page
Reduce the number of public bodies per graph

It seems to be difficult to customize the display of the
tick labels (see the body-statistics-rotated-label branch
for an as-yet-not-working alternative) so for the moment
just reduce the number of public bodies shown per graph
from 10 to 8.
Add some caveats to the experimental statistics page

The statistics we're publishing are potentially subject to
misinterpretation, so add some warnings about their experimental
nature.