Better CP model defaults

Improved defaults for CP model to derive CP
and W' from bests data.
Fix CP defaults bug

.. set to 3600 not 360 (!)

.. updated intervals causing warnings when using values
   that were half baked. Now delays recalc() till all
   the parameter intervals are set.
Plot CP model for derived power series

.. not sure of the validity of applying the model
   to derived data series like xPower and aPower
   but it may provide some insight.
Compare toolbar/menu option

Just added a toolbar button and menu to bring up the
compare pane, before adding it to the tab and view
classes.
Compare button icon