New Metric Fatigue Index

Looks at the max and min (non-zero) power values and
uses the difference between them to calculate a fatigue
index as a percentage.

i.e.
FI = (maxP - minP) / maxP * 100.00;

This is really only useful for targetted intervals as for
most riding there will always be a period of time where
the rider coasts or takes it easy.

We may look to improve it by smoothing or comparing to the
average power instead of minimum power.
Fix 2d crash

Qwt 6.1 seems to delete objects when they are detached from
the plots by default, so we don't delete them after detach
any more in ScatterPlot.
Quadratic Least Squares Trend Line

Added a quadratic least squares trend line for the LTMplot
as the linear regression was generally too blunt.

This is a hack to get the code into the repo -- will know work
on refining the LTMPlot settings to enable users to specify
the kind of trend line they want.

The new trend line might also be useful for other curve fitting
functions (e.g. realtime virtual power curve, a peak power chart
by cadence/pedal speed).
Fencepost error in LTMTrend2

.. missed off the last data point each time!
Revert last commit

.. it wasn't a fencepost error!
Add copyright and fix bomb character in LTMTrend2
Fix LTM axis scale setting

.. dumb bug set all scales to same value!
Accidentally comitted increase in trend points

..was experimenting with fewer and more points on the trend
  line and accidentally committed it alongside the changes
  to fix the LTM axis scale setting.
LTM chart user selectable trend lines

.. now allows the user to select the type of trend
   line for a curve, only two options at present;

   * linear (linear regress)
   * quadratic (quadratic lsm)
ExtendedCriticalPower: Add Model for ExtendedCP
 - One version of the model (Version 4.3)
Autofilter

.. let the user choose metadata texts to filter
   by value in the sidebar.

Note there are issues;

1. the value lists are not updated automatically when
   rides are updated or imported and values are added
   or removed.

2. it only works with shorttext metadata fields, we might
   choose to add numeric etc later.

3. it would be nice to get an indication of how many
   activities contain the value and maybe even sort
   by count.
Fixup SEGV and layout error

.. minor fixups for new CP model code to initialise
   some vars to NULL and remove Qt runtime warnings
   about layouts.
Cosmetics tidy up chart settings
Only show 1 model curve

.. either extended or standard models shown.
Check CPcurve is non-null before hide/show
CPintPlot: Add extendedCP in model combo
ExtendedCriticalPower: Change default
Ignore qwtconfig.pri