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.
This seems like a useful thing, whether for Travis or otherwise. Maybe look for a var called `$FRESH_MONGODB` or something? Then we could use it locally, too.