Test firmware description parsing so far.

The test files come from three locations:
1) ovmf-sb-keys.json and ovmf-sb.json come from OVMF
package from RHEL-7 (with slight name change to reflect their
features in filename too),

2) bios.json and aavmf.json come from example JSON documents from
firmware.json from qemu's git (3a0adfc9bf),

3) ovmf.json is then copied from ovmf-sb.json and stripped
of SECURE_BOOT and REQUIRES_SMM flags, OVMF path change,
description update and machine type expanded for both pc and q35
machine types.
Signed-off-by: NMichal Privoznik <mprivozn@redhat.com>
Reviewed-by: NDaniel P. Berrangé <berrange@redhat.com>
Acked-by: NLaszlo Ersek <lersek@redhat.com>