Add option to skip highlighting if last matched

How it works from the docs:
The ```skip_if_last_matched``` option can be used to entirely skip highlighting
if the last field matched.  This can be used to form "chains" of fields only one
of which will return a match:
```js
  "highlight": {
    "type": "experimental",
    "fields": {
      "text": {},
      "aux_text": { "options": { "skip_if_last_matched": true } },
      "title": {},
      "redirect": { "options": { "skip_if_last_matched": true } },
      "section_heading": { "options": { "skip_if_last_matched": true } },
      "category": { "options": { "skip_if_last_matched": true } },
    }
  }
```
The above example creates two "chains":
* aux_text will only be highlighted if there isn't a match in text.
-and-
* redirect will only be highlighted if there isn't a match in title.
* section_heading will only be highlighted if there isn't a match in redirect
and title.
* category will only be highlighted if there isn't a match in section_heading,
redirect, or title.

This needed to wait until Elasticsearch 1.3 because in 1.2 the fields were
passed to the highlighter in random order.  In 1.3 they are passed in the
order they are sent.  Yay.

Change-Id: I0326baaf497a305348eb536461cd8d6404795d2c