chore(build_library): strip out verity logic

remove some unused verity variables.
chore(build_library): remove efi image

we don't really care about booting on pure efi systems right now and I don't
think this all works so remove it for now.
feat(boot_kernel): add support for the boot kernel

This adds the boot_kernel to the build boot partiton and updates the
relevant config files. Mission accomplished.

TODO: Update the installer to not worry about moving files around
anymore
Merge pull request #39 from philips/use-boot-kernel

Use boot kernel