Windowless border on metric refresh popup
Introduce SB Lowpoint

Let the user define the lowpoint for stress balance -- this is
so we can highlight or alert when they go below.

From a post-hoc perspective it is useful for identifying where
they went too low, but also for planning it helps to stop
planning to fail.

Will update the LTM chart to highlight it alongside SB metrics.
Plot Background and CP chart

If you change the plot background to black then the
CP curve is always in black too so becomes invisible.

Added a customisable color for the CP curve and fixed
up a few redraw issues in CP and Ride plot when you
change the colors.

Still need to fixup the other charts, but will do over
time. I suspect almost noone changes the plot colors from
the default values.
Fix up CP markers

.. to use the right colors.