Incorrect parsing of or/and constraints with more than two literals

[skrieter]

When writing a UVL model with a constraint such as A or B or C, it is correctly written as A | B | C. But when parsing it, it is parsed as (A or B) or C.

Here is a failing test case demonstrating this behavior:

@Test
void multiOr() {
	FeatureModel uvlModel = new FeatureModel();

    Feature root = new Feature("root");
    uvlModel.getFeatureMap().put("root", root);
    
    uvlModel.setRootFeature(root);
    Group uvlRootGroup = new Group(Group.GroupType.OPTIONAL);
    root.addChildren(uvlRootGroup);

    Feature a = new Feature("A");
	Feature b = new Feature("B");
	Feature c = new Feature("C");

    uvlRootGroup.getFeatures().add(a);
    uvlRootGroup.getFeatures().add(b);
    uvlRootGroup.getFeatures().add(c);
    
    uvlModel.getFeatureMap().put("A", a);
    uvlModel.getFeatureMap().put("B", b);
    uvlModel.getFeatureMap().put("C", c);
    
    OrConstraint constraint = new OrConstraint(
			new LiteralConstraint(a),
			new LiteralConstraint(b),
			new LiteralConstraint(c));
    
	uvlModel.getOwnConstraints().add(constraint);
	
	assertEquals(constraint, new UVLModelFactory().parse(uvlModel.toString()).getConstraints().get(0));
}

[SundermannC]

Fixed in #36