build qwt as static library
Merge branch 'master' of git://github.com/GoldenCheetah/GoldenCheetah
Merge branch 'master' of git://github.com/GoldenCheetah/GoldenCheetah
Merge branch 'master' of git://github.com/GoldenCheetah/GoldenCheetah
Merge branch 'master' of git://github.com/GoldenCheetah/GoldenCheetah
Merge branch 'master' of git://github.com/GoldenCheetah/GoldenCheetah
using milliseconds for delta_t when calculating speed, supports Suunto Ambit gpx datafiles
Merge branch 'master' of git://github.com/GoldenCheetah/GoldenCheetah
Histogram Golden Ratio for Zone Columns

.. taking what we did for compare mode and applying
   it to the normal zoned display.
Merge pull request #766 from Walibu/master

Using milliseconds for speed calculation, needed for Suunto Ambit gpx datafiles
Add more Suunto Ambit test rides
Fix PMC LTM SEGV

.. cut and paste error!
Optimise W' calculation

Instead of just reimplementing the spreadsheet we now
implement according to the original formulas as defined
in the W'bal paper.

This means there is no longer a 1200s limit to the decay
which was not part of the original paper.

We should be able to add some W'bal metrics now.
Add W'bal Metrics

Added;
- minimum W'bal == how deep did you go on the ride?
- max match == hardest sustained effort in KJ.

Fixes #760
Added W' Tau as a metric

.. so we can track and see if it correlates with anthing.
Added W' expenditure metric

.. energy spent above CP
Enable use of Minimum W' bal in data filter
Minimum CP for W'bal going negative

.. on ride plot, when W'bal is plotted we put a mesage to say
   that CP is wrong, and autosolve for W'bal to zero.

.. this patch also optimises WPrime to make it a member of the
   ridefile class and this always available (even for intervals).

.. fixed a SEGV when computing metrics for intervals by shifting
   the timestamps to always start from zero.
Fix DIV/0 SEGV with WPrime
Fix temperature curve

Cosmetic fixups to make sure temperature is visible
and the fill is honoured.