ObjectProperty Hydrator should only hydrate public properties (fix + new test)

According to the docs, the Zend\Stdlib\Hydrator\ObjectProperty hydrator hydrates "Any data key matching a publicly accessible property will be hydrated; any public properties will be used for extraction."

This wasn't the case with the system as was. Using the hydrator to populate from form post the property was created for the save button entry. Validating that something wasn't awry I found no test for this hydrator so have 
1. submitted the fix to only hydrate public properties (with exception of stdClass)
2. have created a test for the hydrator

I hope that this meets guidelines for this.
Please use `$this->setExpectedException()` instead.