Split #974 into two PRs - scalastyle updates (#1037)

* Update style warnings now that subprojects are aggregated.
Use "scalastyle-test-config.xml" for scalastyle config in tests.
Enable "_" in method names and accept method names ending in "_=".
Re-sync scalastyle-test-config.xml with scalastyle-config.xml

* Remove bogus tests that crept in with git add

* Add missing import.