Simplify pin output control on heater, fan channels

Since we're hardcoded to two different methods of control for the heater
and fan, and there is no loop, there's no reason we can't just use the
pins for the heater and fan directly. So I do this now. Saves >150bytes.
Add ReflowController\todo.txt

These are the code-side of things I'd like to get done with this
project.
Fix profile load/save can't exit; Made reset harder

- Fixes the bug where you can't cancel loading or saving a profile, or
cancel factory resetting
- Makes factory resetting more difficult by requiring a double-click to
confirm