0.0.9-battery-accuracy#v4.0#SqueezeToo#squeezetoo

The bat_config has been changed to allow a y=mx+b type configuration to get better voltage readings. This makes use of scale and offset parameters. In addition an osd parameter is available to show a battery gas gauge when the lower part on an OLED screen is otherwise unused.

For the SqueezeAmpToo a good bat_config would be:

scale=17.8, offset=1.1, osd

e78ffdf finally get reasonable battery voltages
7647eed finally get battery reading correctly