Ability to apply functions on result set rows as alternative to :result and :keys

Comparable to Clojure JDBC's 'with-query-results', add the ability to apply function(s) to result set rows. Korma in it's currently state is useless when it comes to large result sets, and with this simple patch, at least users have the ability to do so without having to abandon the library.

I only implemented this for exec-raw; I don't think it makes much sense beyond that.

To use, pass a vector of functions to work on rows, like:

    (exec-raw-with refract ["select * from evaluation_templates limit 10" []] [#(println "row: " %)])