Add Power 'heat' to RideFileCache

.. to indicate which power-durations are getting worked hardest

.. Calculate a 'heat' score for the power duration curve.
   A score that counts how many rides in the aggregate
   have a power-duration best that is within 10% of the
   best value calculated.

.. next step is to add it to the CP curve (when showing
   power) to provide some kind of shade/heat indicator
   for the area of the curve.
Fix ButtonBar paint error

.. caused by an eventFilter not returning false and therefore
   always filtering out the events on the chartbar and buttons.
Add Heat to CP chart.

.. from an idea from Michael Puchowiz during discussions
   about a Multicomponent PMC.
CP heat is only below the curve

.. makes it much easier to read and interpret!
Fix Mac SEGV

.. native widget causes issues with 4.8.5
.. rideItem->ride() needs to check rideItem is not null
CriticalPowerWindow: Add a Heat by Date option
CpintPlot: Small correction
CpPlotCurve: Add missing files in last commit
Stress Metric Prototypes

Added a few new training stress metrics whilst discussing
and working on a multicomponent view of training stress.

This is all a wip falling out of discussions around stress
metrics beyond the old TSS/BikeScore models.

For now this just includes;
1. Aerobic Training Impact Scoring System on PM/PMC
2. Work (Kj) above/below CP on PM/PMC
3. Aerobic TISS on the Ride Plot

There is lots more to come; specifically around Anaerobic TISS,
looking again at polarised training and personalised training stress
based upon the individual's CP model.
Aerobic TISS fixup

.. for rides with samples other than 1s recording.
Fix AllPlot SEGV on Compare

.. introduced by a dodgy cut and paste to support the new
   data series Aerobic TISS.
Mouse Over Interval List to Highlight

.. same as hovering over the interval in the ride view
   hovering over it in the tree list now triggers the
   event.
Clear Compare Pane

.. last piece of the jigsaw for compare mode. This update adds a
   clear button to the compare pane bar.

.. we can still add lots more to compare mode, but for v3.1 this
   is probably enough now, so closing the feature request too.

Fixes #343.
QT Mac support is shit

.. making our own buttons to get around the hideous pile of shit
   that is a QPushButton on Mac when you want it to be smaller than
   a billboard sign.
Attempt to fix aPower calculation
CP plot ride as %age of best

.. to quantify the areas trained during the ride
CP pointHover

.. plot the interval on hover in the sidebar.
CP pointHover fixup

.. bounds checking on array index
.. set curve grey not white!
More CP plot fixups

.. allplot color fixed when not a rainbow curve

.. fix SEGV index bounds check off by one

.. hover curve z-order to top
Remove errant qDebug statements