Add a new behaviour to implement a fake relation with data on it

an abstract model is provided to construct the fake relation

A way to use it should be like this (for an orderered relation) :

Class :
```php
<?php
namespace Catalogue;

class Model_OrderMany extends \Nos\Model_DataMany
{
    protected static $_table_name = 'product_gamme';
    protected static $_primary_key = array('gamm__id', 'prod__id');
    protected static $_properties = array(
        'gamm__id',
        'prod__id',
        'prod_order',
    );

    protected static $_has_one = array(
        'product' => array(
            'key_from' => 'prod__id',
            'model_to' => 'Catalogue\Model_Product',
            'key_to' => 'prod_id',
            'cascade_save' => false,
            'cascade_delete' => false,
        )
    );

    protected static $_belongs_to = array(
        'gamme' => array(
            'key_from' => 'gamm__id',
            'model_to' => 'Catalogue\Model_Gamme',
            'key_to' => 'gamm_id',
            'cascade_save' => false,
            'cascade_delete' => false,
        ),
    );
}
```
Model with the behaviour : 
```php
 protected static $_has_many = array(
        'products' => array(
            'key_from' => 'gamm_id',
            'model_to' => 'Catalogue\Model_OrderMany',
            'key_to' => 'gamm__id',
            'cascade_save' => true,
            'cascade_delete' => false,
            'conditions' => array(
                'order_by' => array('prod_order')
            )
        ),
    );

protected static $_behaviours = array(
        'Nos\Orm_Behaviour_DataMany' => array(
            'events' => array('before_save', 'after_save', 'after_delete', 'before_delete'),
            'relation' => 'products',
        ),
    );
```