Fix LTM legend colours

.. when user changes the background color for charts the
   legend can be difficult to read as it is always in black.

.. we now update the legend and it's widgets to change the text
   color when the chart is refreshed.
Fix stylesheet for 'More...' when config changes
Fix SEGV on add chart with Qt5

.. and also selects the first chart on the chartbar at startup.
HrPw honours background color preferences

.. bringing it in line with the other charts honouring the
   background color chart preference.
TreeMap plot honour background colors
PMC Chart honour background
Bing Map honour background

.. and small cosmetic fix for google map to be right colors
   whilst loading the map too .. stop nasty flicker.
3d plot honour background color

.. it already had plot background just needed to honour for
   the frame too.

.. also fixed default empty window to use correct colors.
Always signal when color changed

.. even if changed to same value to ensure the widgets
   are updated to reflect -- especially if setting to the
   same as the default value.
Aerolab honour background colors
Colors.h missing in ModelPlot.cpp