Graph starting at 0 fix, some small fixes for updating GPIOs

Fix to the status recorder that prevents it from storing an initial value of 0.0 for temperature probes that hadn't gotten their first reading yet.

Fixed updating the PID when either a heat or a cool GPIO wasn't set (was getting null pointer). Also fixed an issue where the calibration temperature was being output as 50+ zeroes to the configuration file and couldn't read itself back in