add AdapterManager in to Zend\Db\Adapter namespace

this AdapterManger allows handle multible database connections and aliase

unit tests will follow

```php
#autoload/global.php
return array(
    'db_adapter_manager'=>array(
        'user'=>'global',

        'global'=>array(
            'driver'=>array(
                'driver'=>'Pdo_Mysql',
                'database'=>'my_database_name',
                'username'=>'root',
                'password'=>null,
                'characterset'=>'utf8'
            )
        ),
    ),
);
```

```php
# module.php
    public function getServiceConfig()
    {
        return array(
            'factories' => array(
                'db_adapter_manager' => 'Zend\Db\Adapter\AdapterServiceFactory',
                'my_user_db_adapter' => function ($sm) {
                    $dbAdapterContainer = $sm->get('db_adapter_manager');
                    return $dbAdapterContainer->getAdapter('user');
                },
            )
        );
    }
```

```php
# controller
    public function fooAction()
    {
         /* @var $dam\Zend\Mvc\Service\DbAdapterManager */
         $dam = $this->getServiceLocator()->get('db_adapter_manager');

         if ( $dam->hasAdapterConfig('global') ) {
             /* @var $adapter \Zend\Db\Adapter\Adapter */
             $adapter = $dam->getAdapter('global');
             $dam->addAdapter('news',$adapter);
         } else {
             // do something else
         }
    }
    public function userFooAction()
    {
         /* @var $userAdapter \Zend\Db\Adapter\Adapter */
         $userAdapter= $this->getServiceLocator()->get('my_user_db_adapter');
         $result = $userAdapter->query('SQL Querys',$userAdapter::QUERY_MODE_EXECUTE);
         var_dump ( $result->current );
    }
```