Updates to sorting and mean calculations

Refactoring to sorting and averaging to fix some bugs in the new front page charts.

I also added a showPoints() function to LineSeries to make the points optional. Longer term, this could take an options argument for how the points should be displayed.
This was an old function that I have now removed.  computeFunction() was used to call any user specific code after aggregation, but this is being reworked so I have removed it.