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.
also; should it be extending newstyleplot? i generally want everything to use the newstyleplot API going forward