wic/plugins: Source that support both EFI and BIOS
Add a source plugin that support both EFI and legacy PC-Bios.
While using this plugin, both bootloaders configurations reside
in the same /boot partitions.
This plugin has very little code : to avoid code duplication,
we simply re-import bootimg-pcbios and bootmg-efi source and
call both their SourcePlugin methods.
Signed-off-by: William Bourque <wbourque@gmail.com> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
