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
Merge pull request #302 from elyobo/obey-filters-in-hydration

Adds support for Zend Hydrator Filters in the DoctrineObject Hydrator.