Backported latest improvements and fixes from the SdFat liibrary to our own...

Backported latest improvements and fixes from the SdFat liibrary to our own version. This includes support for CRC7 validation on commands and also, made sure that even if using software SPI implementations, SD card speed is properly adjusted when transitioning from INITIALIZATION to DATA TRANSFER mode. ALL HALs implement spiInit, even in SW SPI mode, and we NEED this change to improve 25x the transfer speed of the SD card and allow implementations of USB MSD