Add metrics showing the number of events evaluated

[jwomeara]

We save statistics for the number of next, seek, and fi ranges we see for a given query. We should also save statistics for the total number of events we evaluate for a given query. This would give us useful insights into the number of events returned vs the number thrown away during evaluation. This could help to explain queries which tend to run longer for seemingly no reason - the theory being that they are spending a lot of time throwing away potential matches.

Whoever works this ticket should 1) update the query iterator to save off the number of events evaluated and return that information to the webservice, and 2) update the query metric html page to display the number of events evaluated, and the number of events rejected.