Truncate text operates on entire length of aggregated multi-value fields in list output

[dantleech]

e.g.

| phpcr:class        | STRING        | Symfony\Cmf\Bundle\RoutingAutoBundle\Model\AutoRoute |
| phpcr:classparents | STRING        | [0] Symfony\Component\Routing\Route                  |
|                    |               | [1] Symfony\Cmf\...                                  |

[dantleech]

Will be fixed with #83