(PDB-1011) Allow querying of PDB directly via a TK service

This commit adds a function to the PuppetDBServer service to execute a
query and return the results as a Clojure data structure (rather than
streaming JSON over HTTP). A function can be passed in that will accept
a lazy seq to consume the rows
I'm not sure exactly what you're testing when you comment part of the test out, but if there are no facts, it returns an empty vector. You can't call realized? (I'm doing this in the test) on an empty vector. What are you trying to test?