qemu-io: allow specifying image as a set of options args

qemu-io: allow specifying image as a set of options args

Currently qemu-io allows an image filename to be passed on the
command line, but unless using the JSON format, it does not have
a way to set any options except the format eg

 qemu-io https://127.0.0.1/images/centos7.iso
 qemu-io /home/berrange/demo.qcow2

By contrast when using the interactive shell, it is possible to
use --option with the 'open' command, or to omit the filename.

This adds a --image-opts arg that indicates that the positional
filename should be interpreted as a full option string, not
just a filename.

 qemu-io --image-opts driver=https,url=https://127.0.0.1/images,sslverify=off
 qemu-io --image-opts driver=qcow2,file.filename=/home/berrange/demo.qcow2

This flag is mutually exclusive with the '-f' flag and with
the '-o' flag to the 'open' command

Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>