[pie-dev] Adding basic doc and constructor

Adding the constructor, files, and basic documentation for a pie plot.

Note: I am trying to use the feature branch model in order to incrementally commit things so breakages are less probably downstream.  Thus, I might have pull requests that seem arbitrarily too small or too large.  I'm calibrating as time goes on.

Note:  Note the target branch.  This is not to develop.
I want to use the addDataset model.  However, because newStylePlot doesn't extend from plot itself, I have no access to it.