bump(coreos-base/cros-devutils): Now includes chromeos-common.sh

This file was previously installed by the coreos-installer package.
fix(coreos-base/*): Clean up cros-installer and cros-factoryutils

cros-installer has already been removed, clean up lingering references.
cros-factoryutils installed nothing, just remove the ebuild.
Merge pull request #412 from marineam/quickfix

Fix cros-installer removal