configs/releng/build.sh:
Copying the edk2-shell based Shell_Full.efi to the root of the iso/ efi
image as 'shellx64.efi' is automatically picked up by certain hardware
and by systemd-boot.
This makes all custom UEFI shell configuration obsolete.

configs/releng/efiboot/loader/entries/uefi-shell-*.conf:
Removing obsolete custom UEFI shell boot loader configuration.

Closes #14