Adds support for Zend Hydrator Filters in the DoctrineObject Hydrator.

Zend Hydrators normally support [filters] [1] to modify the results returned.  This patch adds checks for filters on a property name basis back into the hydrator.

A sample filter is also included, which implements simple whitelisting and blacklisting of property names.

Tests are included applying this filter during extract by reference and extract by value.

[1]: http://zf2.readthedocs.org/en/latest/modules/zend.stdlib.hydrator.filter.html