Fix cascading when deleting a node

[nlzet]

When deleting a node cascading operations are not executed, because a delete query is used. This fixes this problem.

See: http://doctrine-orm.readthedocs.org/en/latest/reference/dql-doctrine-query-language.html#delete-queries

[Rene-Sackers]

Bump? Can we please accept this please? This issue keeps popping up in my projects,