The old options are still supported for compatibility, but they are
inconsistent (for example create -b vs. convert -B for backing files) and
incomplete (-F only exists for create) which tends to confuse people. Remove
all references to the old options from the documentation to guide users to the
more consistent -o options.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>