added configurability for MCU and SPI peripheral
fork spi into two separate sets depending on whether g2452/2231 or g2553 is used
check for USI/USCI definition
comments and target for help
suppress shell commmands on targets
check for USI/USCI defintion
enter and stay in LPM3 except in ISRs
better target 'clean'
even, even better target clean