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
Yep, earlier on I tried to replace the for loops with a more readable map(function(){}) style but I noticed a drastic performance hit when I was clicking on the charts.

These reduce functions are called a lot, so in here I'm using cached for loops.  In other parts of the code, forEach() should do and also make things more readable