usbboot: no longer 32-bit specific

+ add '-c /dev/null' to ignore blkid caching
usbboot: correctly tell the user to press ENTER not ANY KEY
usbboot/isolinux.cfg: v1.0.1 release
usbboot/install-ubuntu: safer 32/64 bit CPU checking

+ before we could accidentally double-count and default to 32-bit
+ this means false negatives (for 64-bit) probably occurred, but 0 false positives
usbboot/install-ubuntu: safely wait for any pending udev events
usbboot: change image label, on boot wait for USB to become visible

+ this should fix #1
usbboot/isolinux.cfg: 1.1 release