Fix incorrectly resolved merge conflict.
Improve AVR Uart and UsartSpi baudrate calculation.
Rename I2cDelegate to I2cTransaction.
Refactor transaction methods for pass-by-reference.
Rename size to length in I2cTransaction structs.
Update AVR and software I2C implementations.
Rename SpiDelegate to SpiTransaction.
Refactor transaction methods for pass-by-reference.
Update software SPI implementation.