(PE-2168) Produce a test utility code jar

This moves the test utility code from src/ and into test/
and changes the project to produce a -test jar alongside
the production jar with all the test utility code in it.
Projects can then utilize this test code by adding a
kitchensink dependency with a "test" :classifier.
Merge pull request #10 from nwolfe/dev/master/produce-test-jar

(PE-2168) Produce a test utility code jar