This adds a new livemedia-creator argument, --extra-boot-args, which can
be used to add arguments to the kernel command-line in the templates.
Resolves: rhbz#1689314
This adds the aarch64 template, and the grub2-efi config file to the
live template directory.
Resolves: rhbz#1369014
(cherry picked from commit 89c7a93508b7328fc9c180164b23fae29bcd022b)