Add command for setting switches for potentiometry (pot_exp_start()). Add pot_experiment() for acquiring voltage measurements from RE input for potentiometry or OCP. (currently not called anywhere)

Initial implementation of preconditioning. Still a dummy function, needs to be added into main.c for each experiment command handler.

Added CSWV functionality to SWV. **Incompatible with dstat-interface commits before 1155414, due to extra scans variable added.** Changed the data output timing. Seems to still work, but need to check with electrochem.

Renamed chronoamp function to ca_experiment. Finished command handlers. Adapted CA handler to use dynamic allocation.

Changed autogain defines to external vars. Basic gain implementation. autogain_enable global controls whether autogain breaks early. Simplified over/undercurrent compare calculation.