Don't patch grub2 or grub2-signed

[codygarver]

May be able to make modifications without carry patches, which would be living the dream since this is the patchload that breaks down most often.

[codygarver]

Tasks to make this happen:

• Create /etc/grub.d/06_elementary_theme during iso build so that parts of 05_debian_theme get overridden
• Create /etc/default/grub with desired values like GRUB_TIMEOUT=5 during iso build
• Upstream modification of Ubuntu's grub2 install_efi_ubuntu_flavours.patch that treats elementary case like kubuntu (See https://bugs.launchpad.net/ubuntu/+source/grub2/+bug/1242417)
• Upstream modification of Ubuntu's grub2 mkconfig_ubuntu_distributor.patch that treats elementary ${GRUB_DISTRIBUTOR} case like Ubuntu|Kubuntu so it does not append GNU/Linux to boot entry