Simplify the implementation of configmix.load() and .safe_load(): this also prepare for the coming implementation of a "last" user configuration (analogout to "defaults" as the first configuration).

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