Fix some SPI bit bang timing.  I still don't think it is working properly; I am going to need to borrow a logic analyzer

Revise how delays are calculated in SPI bit bang driver so that we may get a little better frequency resolution

Add a general bit-bang SPI lower-half driver and implement the bit-bang driver for the Arduino ITEAD TFT shield

Add an NSH configuration for the Arduino Due; Pluse several fixes related to the Due and to the SAM3X in general

Arduino Due: Fixes to FLASH address, flash wait states, updated Comments.  Now boots and runs a bit before crashing

Flesh out the Arduino Due board configuratino and integrate it with the build and configuration system