Move away from destructuring query terms, and create separate arities for terms which include optargs

[danielcompton]

I'm not sure how important or necessary this is, but there is a fairly large performance hit for destructuring optional arguments in functions.

For example:

(defn changes
  "Return an infinite stream of objects representing changes to a query."
  [xs & [optargs]]
  (term :CHANGES [xs]))

takes roughly 200 ns to run when passed an optarg, whereas

(defn changes
  "Return an infinite stream of objects representing changes to a query."
  ([xs]
   (term :CHANGES [xs] nil))
  ([xs optargs]
    (term :CHANGES [xs] optargs)))

takes ~25 ns. While the speedup is large in relative terms, it's still fairly small in absolute terms.