optional user and password in config

Using DB2 over JDBC brings problems when the username and password are to be configured within the connection url.

Solution is to call Drivermanager.getConnection(String url, String user, String password).

Also, the dependency to java at version 0.4.3 breaks the build on windows pc's becaus of a compiler error.
See https://github.com/joeferner/node-java/issues/169 for details.
Reverting to java version 0.4.2 fixes the build.