Add ability to order by terms

[kurtado]

Within a terms aggregation visualization, currently you can order by "Metric:count" and "Custom Metric". It would be nice to add the ability to sort by the terms themselves via the dropdown, e.g.

{
        "order": {
          "_term": "asc"
        }
}

http://www.elastic.co/guide/en/elasticsearch/reference/current/search-aggregations-bucket-terms-aggregation.html#search-aggregations-bucket-terms-aggregation-order

Spoke with @spalger about this earlier today.

[jimmyjones2]

Same as #1980?

[spalger]

Yep, you're right @jimmyjones2