fix: use CoreSetup*.class instead of (new Object()).getClass())

The initializeLogging() method used this code to load the given logging
configuration resource:

(new Object()).getClass().getResourceAsStream(loggingProperties))

However this made problems loading the resource with
"/logging.properties" when running Nifty from the commandline using code
like:

mvn exec:java -Dexec.mainClass="some.Main"

I suppose there is a problem with some class loaders since the original
code uses the classloader of "java.lang.Object".

I've now changed it to "CoreSetupJogl.class.getResourceAsStream()"
directly which seems to fixed my issue.

@Brian: can you comment on this? What's the purpose of (new
Object()).getClass() instead of using a class directly from the package?