Expand references in phpcr:dump

This PR expands reference in the PHPCR dump to change:

````
./app/console doctrine:phpcr:dump /cms/chronology --props 
  2011-01-20:
    - references = Array(    [0] => 78b6f31b-f72a-4514-8f9d-b6e4a6786134    [1] => 896a3903-2614-4f8d-
8543-0758022aaa4d    [2] => 43d60...
    - phpcr:classparents = Array()
    - phpcr:class = DTL\TravelBundle\Document\ChronoDate
````

to 

````
./app/console doctrine:phpcr:dump /cms/chronology --props --expand-references
  2011-01-20:
    - references = 
       - ref: /cms/content/DTLs Blog/aut-molestiae-rerum-eum-eius
       - ref: /cms/media/e6d2cab1959d05eeeec8ebe6bb3f1f3068e89f4e.jpeg
       - ref: /cms/media/49c33d6063f1ad0f3d4a3aa7d09b986c4ccddd02.jpeg
       - ref: /cms/media/34f453a6b65d58345e1ff639b5714da451698178.jpeg
    - phpcr:classparents = Array()
    - phpcr:class = DTL\TravelBundle\Document\ChronoDate
````

This is really good for debugging, not so sure on the name of the option however. I also wonder if we shouldn't list `array` properties in a similar way.