Returns supply voltage of Arduino board
Based on the code by sweebee
https://github.com/sweebee/Arduino-home-automation/blob/master/libraries/readVcc/readVcc.h
Node for writing to ViSi-Genie scope object. Node has a DONE pulse output to facilitate chaining writes. Minor extension to gabbapeople/4d-ulcd and bradzilla84/visi-genie-extra-library.