bump(coreos-base/vboot_reference): small cgpt update
bump(coreos-base/cros-devutils): Various fixes for /usr images.
fix(sys-kernel/coreos-kernel): Install kernel image to /usr/boot

/boot is not included in /usr images
remove(coreos-base/coreos-installer): replaced by a small shell script

The tools this provided are moving to update_engine.
bump(coreos-base/update_engine): Support for /usr images