[Improvement] "10-nashorn.md" - Add objects manipulation examples (extend/merge)

For my project I need to extend objects, so normally I use external libraries for example `jQuery.extend(...)` or `lodash.merge(...)`:

``` javascript
// test "lodash" lib
var test = {id: 1};
var test2 = _.merge({}, test, {name: "Bob"});
print(JSON.stringify(test2));
```

Do you know a Java-native way to extend objects? for example using `ScriptObjectMirror.putAll(...)`
