Get rid of attributes of type LIST of PROPERTY; use OBJECT of STRING

A read-resource-description output of a standalone-full-ha.xml server (see attached) shows a couple attributes that are of type LIST, value-type PROPERTY. (Just text search for PROPERTY.) We should convert those to OBJECT, value-type STRING. Both represent a resource address. An object of string is equivalent to a LinkedHashMap<String, String>, with ordering based on insertion. So such a description is fine for a path address attribute.

I'd like to get rid of the notion of PROPERTY in our spec definition of how to describe attributes, parameters and value-types (https://docs.jboss.org/author/display/WFLY/Description+of+the+Management+Model) so removing the only usage of it will help.

We should still accept PROPERTY as inputs when we can do conversion to the defined type. This is all about tightening up the spec to remove the not-really-necessary PROPERTY concept.