improve build process, part of #481

fix oneJar code coverage issue (coverage info corrupts JAR), test built SlamEngine JAR, allow environment variable overrides of backend-config, modify travis to use local mongodb override, auto-import zips data set when in travis builds. note: publish script has not been updated and jenkins is no longer expected to work.
Yeah, I just realized that Travis `services` feature will launch 2.4, which is why the tests are failing. I'm working on downloading, installing, and starting up MongoDB 2.6 manually in the `before_script` section of `travis.yml`.