Support EFI that only boots Windows

[noryb009]

As mentioned here, some systems only boot /EFI/Boot/bootx64.efi (and perhaps even /EFI/Microsoft/boot/bootmgfw.efi). If a user encounters this, there should be an option in the menu (with at least one confirmation box) to install LICK to /EFI/Boot/bootx64.efi.

[noryb009]

This option should:

• Warn the user
• Install the bootloader normally, if not already installed
• (Start atomic operation)
• Copy /EFI/LICK/* to /EFI/Boot/
• Copy /EFI/Boot/bootx64.efi to /EFI/Boot/bootx64-windows-backup.efi
• Move /EFI/LICK/grubx64.efi to /EFI/Boot/bootx64.efi
• Move /EFI/Microsoft to /EFI/Microsoft-backup (this step is required)
• (End atomic operation)

Additionally, while uninstalling the bootloader, this configuration should be detected and reverted. If a partial configuration is detected, use /EFI/Microsoft/boot/bootmgfw.efi as /EFI/Boot/bootx64-windows-backup.efi, or otherwise disallow uninstalling.

[noryb009]

69a1f0d added support in the library and GUI.

Reinstalling reverts the fix, which is tracked in #13.
CLI menu support is not implemented, but CLI flag support will be need to be added when adding support for reinstalling.