'Better' sorting of results by score
Further annotation on the keys that we receive in a result doc
Pull out the code that cleans up an ES result, make it a function
Bail out of the rendering loop much earlier if we see a deleted RT ticket
We've proven that the ES highlighter works, switch to sane highlighting tags
Fix up ES highlighting parameters in the query

The excerpt field was being given too much priority, always being
included even if it didn't contain any search terms. Provsys docs
always contain the search term, but things like wiki pages and RT
tickets often won't.

As an aside, documents arguably shouldn't need an excerpt field now that
ES will extract and highlight matching fragments for us.

These changes mean that the excerpt-highlight will only be populated if
there's a real match. The blob field remains as a fallback and *will*
always contain content, although I *think* it's possible for it to not
be highlighted (if the no_match_size kicks in).

The renderer prefers to display the excerpt-highlight if it exists,
otherwise it displays whatever the blob-highlight has to offer.
Remove useless check for other_metadata in ES results

other_metadata is now guaranteed to be in all results that ES returns,
it's just the contents of _source
We're now making use of Elasticsearch's highlighting results, woohoo!
More comments on the data types passed downstream for rendering
Web frontend can now specify the hit_limit, and use of the MAX_HITS config parameter has moved to the frontend