Change I2C addresses from uint8_t to I2CAddress, in preparation for MUX support. Currently, by default, I2CAddress is typedef'd to uint8_t.
MUX support implemented for AVR and Wire versions.
Timeout handling and recovery in loop() function now operative.
Start-up check for I2C signals short to ground added.
Initial I2C device probe speed up.
Possible infinite loops in I2C AVR native driver during fault conditions removed.
