Implemented the "ref" namespace to get configuration tree references. BUGS: - Tests should be done more thoroughly and extensively - Interaction of tree references and variable substitution should be tested more properly - Documentation is missing yet

{"__comment1": "Comment 1",
 "key1": "the value",
 "key2": 2,
 "key3": 5.7,
 "key4": true,
 "key5": false,
 "key6": 255,
 "__comment2": "Comment no 2",
 "key7": "Umlaute: ÄÖÜäöüß"
}