Moved sys filesystem 'stuff' into its own 'module' - sysfs.h|cpp with system tests and refactored pin_alloc implementations to suit.
Changed so open_collector example will continue doing its thing until users presses enter on console and to have the open-collector output track the value from an input GPIO pin.
Added more complex variation of leds_and_switches example in which the least significant digits of the count are also displayed on a 2-digit 7 segment display with multiplexed segment control lines.