section config: allow full property-isolation for plugins

section config: allow full property-isolation for plugins

When using 'init(property_isolation => 1)', the code saves the
property lists per type instead of a big one, and using
create/updateSchema creates a new schema with the options as 'oneOf'
and/or 'instance-types' (depending if the schemas match).

With that, we change how we work with the options hash:

It's not needed anymore to specify options that are specified in the
type specific propertyList, except if it's 'fixed => 1' (since that does
not exist in the schema)

Signed-off-by: Dominik Csapak <d.csapak@proxmox.com>
 [ TL: ensure consistency with new property-isolation terminology ]
Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>