Pie charts that don't add up to 100

[BenMcLeanHRBlock]

Epoch pie charts should be able to display values which don't add up to 100. For instance, if there's only one data item and it says 42, then we should be seeing a 42% slice of pie and the rest blank. Currently, when I try this, the pie chart fails to render.

Also, it would be nice to be able to display a big number in the center of a donut chart. Lots of people seem to want that on their web sites these days.