[CA] [CA11] display system voltage on axiom 9

[Dan_Y]

I placed the system voltage data item overlay on the chart app in small font to monitor the house voltage. I read about a 3% lower voltage at the Axiom 9 chart plotter compared to the house bank voltage. That seems a bit large for a 20 foot one way run, assuming the Axiom 9 is drawing 0.7 A, although the voltage is well within its voltage operating range.