ads1255: added function for single reads. Changed dummy SPI byte to avoid conflict with ADS1255 SDATAC command.

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)

Conflicts:
	DSTAT-temp/src/config/conf_usb.h
	DSTAT-temp/src/experiment.c
	DSTAT-temp/src/main.h
	DSTAT1.atsuo

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.