Cuboxi: remove old boot file
Cuboxi: remove project specific update.sh
u-boot: added create_sdcard script for u-boot booted devices.

Includes work from @soul9 and Wandboard
u-boot: added files to support new u-boot
u-boot: added update.sh script
u-boot: cleanup old files and added u-boot specific update.sh script
Merge pull request #3209 from jenkins101/cuboxi-boot

u-boot: bootwork