[imp] JArrayHelper::toObject allow non-recursive conversion

Tracker item:
http://joomlacode.org/gf/project/joomla/tracker/?action=TrackerItemEdit&tracker_item_id=33902&start=0

The default mode of the function `JArrayHelper::toObject` is to recursively convert any subarray in another object of the same specified class. I would say this makes no sense in 99% of the times.

This PR adds a way to use the same function but without subarray conversion.

Let's say that you have an array like:

```php
$array = array(
	'prop1' => 'value1',
	'prop2' => 'value2',
	'prop3' => array(
		'subprop1' => 'value1',
		'subprop2' => 'value2'
	)
);
```

Current conversion is used like:

```php
$converted = JArrayHelper::toObject($array, 'JObject');
echo '<pre>';
print_r($converted);
echo '</pre>';
```

Result:
```
JObject Object
(
    [_errors:protected] => Array
        (
        )

    [prop1] => value1
    [prop2] => value2
    [prop3] => JObject Object
        (
            [_errors:protected] => Array
                (
                )

            [subprop1] => value1
            [subprop2] => value2
        )

)
```

As you see prop3 is converted to `JObject` too. That's most of the times a non-desired behavior but now it's forced.

I added a new parameter to the function with default = true to keep BC but allowing us to convert only the main array to the desired object keeping the rest children subarrays with their original values. So a call like:

```php
$convertedNonRecursive = JArrayHelper::toObject($array, 'JObject', false);

echo '<pre>';
print_r($convertedNonRecursive);
echo '</pre>';
```

Will show:

```
JObject Object
(
    [_errors:protected] => Array
        (
        )

    [prop1] => value1
    [prop2] => value2
    [prop3] => Array
        (
            [subprop1] => value1
            [subprop2] => value2
        )

)
```
## Test instructions

`JArrayHelper::toObject ` is mainly used in the models `getItem()` function so after applying the patch ensure that all is working. You can also use this sample code:

```php
$array = array(
	'prop1' => 'value1',
	'prop2' => 'value2',
	'prop3' => array(
		'subprop1' => 'value1',
		'subprop2' => 'value2'
	)
);

$converted = JArrayHelper::toObject($array, 'JObject');
$convertedNonRecursive = JArrayHelper::toObject($array, 'JObject', false);

echo '<pre>';
print_r($converted);
print_r($convertedNonRecursive);
echo '</pre>';
```

That will show that the function is stil lBC and the new feature.