Explore build integration with sonarqube

gradle has a plugin to invoke the sonar runner: http://www.gradle.org/docs/current/userguide/sonar_runner_plugin.html

And apache has a sonar server: https://analysis.apache.org/
Setup instructions: https://wiki.apache.org/general/SonarInstance

One upside is that we will gain a dashboard for code quality of the python build, unified with possibly-overlapping but still useful metrics for the java build.