More updates (#26)

* Overvoltage work

* Update firmware rev to 1.2

Add calibration feature, scaling balancing thresholds (#25)

* Balancing and Charging Fixes

* Add Calibration Feature

* Upgrade to STM32 HAL 1.2.0

* Tighten Balancing Voltages

* Add firmware version. Increase USB PD request delay.

* Update firmware version printing. Increase stack sizes.

* USB PD request logic. Lower min ADC reading thresholds. Charging power calculation work.

* Makefile (#24)

This PR adds a makefile to the project to enable building the firmware on a linux command line.

* Add balacing scalar functionality

V1.0 Release

Usb pd work (#18)

* Default to 5V

* Basic voltage selection working

* USB PD Charging MVP

* Add max current

* Remove stdlib