Fixup Compare Drag-N-Drop

We have two new mime data types;

application/x-gc-intervals
application/x-gc-seasons

With packing routines into QMimeData declared
in IntervalTreeView and SeasonTreeView.

To get around an issue with overwrite mode on
drag and drop from the seasons / interval trees
we DO NOT ACCEPT the drop (even though we do
actually process the data).

All we need to do now is unpack the QMimeData in
ComparePane and then add the GUI elements to it etc.
CPintPlot: Correct AxisScale for IntervalCurve (eg. HeadWind)
Fix compile error on stackZoomWidth

Gareth's build system baulked at the stackZoomWidth
class member defined as const in the class declaration.

Moved to a static member of AllPlotWindow.cpp instead.
RideNavigator no scrollbar on QT5

No need to adjust sizes to account for a scrollbar
on Mac in QT5, since the scrollbars are zero width.
oopsie on #ifdef

.. too Mac centric in last commit, forgot we might need to
   worry about other pesky operating systems.
AllPlot: Handle noTemp with no smooth
fix #634
AerobicDecoupling: Correct formula
fix #721
MainWindow Refactor Part 5 of 5 - TABBED ATHLETES

The final part (and one of the reasons) for the mainwindow
refactoring -- we now support tabbed athletes rather than
having a new mainwindow for each athlete opened.

Context is saved/restored and there are new functions for
opening and closing tabs and windows of tabs.

The tabbar itself is fugly -- the next few days will spend
some time looking at making it prettier on Linux/Win and
more native on Mac (see MMTabBar).
Missing <QStackedWidget> in MainWindow.h

.. needed to build on QT5
merge upstream into master