Replace libuuid with util-linux libuuid (and libblkid,
although we are not using libblkid right now).
This also requires a much larger coreboot cbfs, which was
fixed as part of issue #154.
This addresses multiple issues:
* Issue #63: initrd is build fresh each time, so tracked files do not matter.
* Issue #144: build time configuration
* Issue #123: allows us to customize the startup experience
* Issue #122: manual start-xen will go away
* Issue #25: tpmtotp PCRs are updated after reading the secret
* Issue #16: insmod now meaures modules
