1.3.1-rc.1+ change to Boron solar charging (via VUSB) behavior

[Rftop]

@epbwhiz

That is a great little unit test you’ve laid out @Rftop. I have the requisite hardware kicking around - could I convince you post a couple of code snippets to save me bumbling through it this weekend?

@epbwhiz, here's a link to the Thread I started w/ Hardware and Code:
https://community.particle.io/t/boron-solar-charging-with-1-5-0-rc1/54680?u=rftop