The config file can now specify options for lorax per variant and arch.
This is needed for Fedora to set x86_64 images as bootable on mac.
The old config option `buildinstall_upgrade_image` was deprecated, as
the same can be specified via new `lorax_options`.
Documentation and tests are updated.
Signed-off-by: Lubomír Sedlář <lsedlar@redhat.com>
716b2d521a