this originated from a misunderstanding of mine going back
several years. the values need not be float64 just because
we plan to serialize them as json.
there are still larger questions about what the right type should
be, and where should any conversions go. but, this commit
simply attempts to address the most egregious problems
This is a change in search result behavior in that location
information is no longer provided by default with search results.
Although this looks like a wide-ranging change, it's mostly a
mechanical replacement of the explain bool flag with a new
search.SearcherOptions struct, which holds both the Explain bool flag
and the IncludeTermVectors bool flag.
