Metric Aggregator Model Refresh (Part 3b of 3abc)

.. added to LTM and updated the default layout on trends view
   to include a new 'CP History' chart with W', CP and p-Max
   on it.

.. part 3c needs to update to include Damien's model and also
   once thats done we need to refactor CPPlot to use the new
   PD model classes instead of the code embedded in the class.