#6 change separator in URI's for Java classes

[Jean-Marc Vanel]

The separator in URI's for Java classes is currently _ , which is bad, as _ can be in class and package names in Java.
We should switch to - .
In class Instanciator there is a constant N3_JAVA_PATH_SEPARATOR .

But several things are hard-coded and dependant on it : other code ( search for "javax_" and "java_" ), tests, examples, swing rules in Déductions project.