Object iterators added.

Added support of object property iterators, e.g. `for (key in obj) {...}`

Notation is similar to array iterators, '@' char is used instead of '~':

```javascript
{{@ {one: 1, two: 2, three: 3} :val :key}}
	{{=key}} = {{=val}}
{{@}}
```

Also, this can iterate only own properties – with additional '@':

```javascript
{{ obj = (function() {
	function O() {
		this.four = 4;
	}
	O.prototype = { one: 1, two: 2, three: 3 };
	return new O;
})(); }}

{{@@ obj :val :key}}
    {{=key}} = {{=val}}
{{@@}}
```