removed constant, and compare less than equal. saves 8 bytes.
OneWire paraside mode compile time flag. We don't use it.
channel sensing for DS2413.  docs, and some tidyup/code size optimization.
improved error detection on write. This can be used by clients to detect serious conditions with actuators that are no longer reachable due to bus failre/disconnection.
moved non-trivial access methods to cpp file. saves 20 bytes. (and potentially more in future as we introduce Onewire switch sensors.)
support for switch sensors on DS2413 (i.e. read from PIO).  Compile-time excluded by default to save 110 bytes.