Made some good progress on secure booting on the SabreLite platform.

While the SabreLite platform from Boundry Device is getting rather long in the tooth. It is one of the (presently) unsupported platform for Windows IoT Core. I have put in a great deal of time and I now have, at least, a secure u-boot implementation working. I plan on doing a pull request to the private Microsoft repo soon. Just a few more pieces to check out. I anticipate the next steps to be not as difficult as there are some good templates to follow. Stay tuned…