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.
It is not part of this PR, but when it is the task of the user, he should get the possibility to use it. So we should make have the chance to pass that values from phpcr-odm i.e. which would be a "user" and implement the chance there.