reduce queries for fetching many node`s data

As described in the cmf-mailing list (https://groups.google.com/forum/#!topic/symfony-cmf-devs/Bv3REKYwT80), this would be my first changes for reducing queries. There is still an test issue i will solve later.
oh its just that row:
```
(
    [path] => /
    [parent] => 
)
```
where there is no entry in the data array.