Order pie charts with biggest category first

The UI shows the label of the first category of a pie chart
in the center of the chart. At a glance this always looks like
it's linked to the biggest colour on the chart. By ordering
so that the biggest category is the first, we ensure that
this visual link makes sense.
Order some pie charts by category, make initial label the biggest cat.

For some pie charts it's useful to have all the categories in a
consistent order for comparison between places, such as gender
or charts that have a small number of cats that will always be present.
For those, order by category but use data-initial-sort to ensure
that the initial label is always the biggest value.

Service delivery charts should have 4 items each, not 3.
Merge pull request #40 from Code4SA/order-pies-decreasing

Order pie charts with biggest category first