Add array_sort helper

The array_sort helper ("array_sort" may be too vague...) sorts a multidimensional array by a column value.

For example:
```
$data = array(
	array('name' => 'baz'),
	array('name' => 'foo'),
	array('name' => 'bar')						
);
return array_sort($data, 'name'); 
```
Would return the nested arrays in ascending order by the value of the 'name' column.

```
Array
(
    [0] => Array
        (
            [name] => bar
        )
    [1] => Array
        (
            [name] => baz
        )
    [2] => Array
        (
            [name] => foo
        )
)
```

The optional $order parameter could be converted to an array later on to allow for more sorting options like numeric vs string sorting. For now, it just accepts a string of 'asc' or 'desc'...