Supporting order in TermsAggreagation like array to allow multi-ordering

[rusboy]

Examples:
Before:

            "terms" : {
                "field" : "fieldname",
                "order" : {"order1" : "desc"}
            },

Now:

            "terms" : {
                "field" : "fieldname",
                "order" : [{"order1" : "desc"}, {"order2" : "desc"}, {"order3" : "desc"}]
            },