Compatibility with JOpt 4.6

JOpt 4.6 redeclared its nonOptionArguments() method from List<String> to List<?>, requiring us to select String arguments only as we do for regular option values already.

Issue: SPR-11359
Consistently declare @SuppressWarnings("serial") instead of dummy serialVersionUID
Upgraded SLF4J, JOpt, JRuby, Commons Pool & Commons DBCP to latest versions