Number of snippets in highlighting. Error if there is no id specified on...

Think number of snippets might be helpful for some projects. What you might be put off by is the change of "highlight" to "highlights" in the document map and the use of an error if there is no ID specified when returning the highlighted values.

The reason for the error is that first time users may wonder why the results are blank when not specifying an ID (although it's kind of in the docs).