Document the ordering property for array and object parameters

[fdrozdowski]

I believe that was implemented as part of this: http://reviews.delphix.com/r/24143

see https://gitlab.delphix.com/platform-plugins/ebs-gate/blob/master/ebs122-app/main.json for another example

I have verified the ordering still works in python plugins.

┆Issue is synchronized with this Jira Bug by Unito