Improved PID Control
- Completely rewritten PID control for tighter tracking against target temperature (when freshroastsr700 is instantiated with thremostat=True).
- Callback functions for update_data_func and state_transition_func now called from a thread belonging to the process that instantiated freshroastsr700. This was necessary for Openroast version 1.2 code refactoring.
- Reduced processor load for PID control as part of code refactoring.