Add Last 2 Months to Seasons

.. jump from 38 days to 3 months is a bit much
Add HrPw Metric

.. as a ratio of Average Power to Average Heartrate
   hrpw = ap / ahr
Add HrNp Ratio

.. to echo HrPw
CPPlot: correct xBttom axis ticks
CPPlot: Power zone shading for watts/kg
merge upstream into master