ICS-46 : Post aggregation reintroduced and general Grouping refactor


You can test the postAggregation function in the Pareto example which calculates a total value and then group percentages:

http://stavrakakis.github.io/insight/#/example/pareto

I also fixed a couple of bugs introduced into the bullet chart by a recent pull request
I would have used logical && here instead of bitwise & so isFinite will not be evaluated if isNumber is falsey.  Also see this for why bitwise & is discouraged: http://stackoverflow.com/questions/7310109/whats-the-difference-between-and-in-javascript