coding style polishing

Remove most checkstyle complaints:

Priority wishlist:

1. Each variable declaration must be in its own statement. [MultipleVariableDeclarations], b/c this really enhances readability and could trip some IDEs when refactoring variable names.
2. '' should be on a new line. [OperatorWrap]
3. Missing a Javadoc comment. [JavadocMethod]
4. others

It still needs to be verified, if our exceptions from Google-style are reflected in the checks. If not, metrics_checks.xml has to be changed accordingly.