New Whitelist / Blacklist Filter

This new filter will behave either as a blacklist or a whitelist. If the value being filtered exists in the list of known values, the filter will return the value if its a whitelist or `null` if its a blacklist. The opposite will happen if value is not in the list.

### Whitelist
```php
$whitelist = new \Zend\Filter\Whitelist(array(
    'list' => array('allowed-1', 'allowed-2')
));
echo $whitelist->filter('allowed-2');   // => 'allowed-2'
echo $whitelist->filter('not-allowed'); // => null
```

### Blacklist
```php
$blacklist = new \Zend\Filter\Whitelist(array(
    'type' => 'blacklist', // optional, default is 'whitelist'
    'list' => array('not-allowed-1', 'not-allowed-2')
));
echo $blacklist->filter('allowed');        // => 'allowed'
echo $blacklist->filter('not-allowed-2');  // => null
```

### Notes  

1. Maybe calling the filter class `Whitelist` might be counter-intuitive if the desired behavior is that of a blacklist. But I couldn't think of a better way to name the filter, so I'm open to suggestions:
    * Something like "AllowedList" would just be a synonym of "whitelist". 
    * "List" would just be too vague.
    * Separate filter classes seemed overkill.
2. I decided to allow only one type of configuration in the constructor (by array of options) just to keep it simple. If you'd like to allow for a more dynamic constructor (like a few other filters do) let me know.
3. Not sure what commit edbc12b is doing in this PR. Looks like its in `master` but not in `develop`.

See #6960 for more info.
The reason I chose "list" instead of "haystack" is that "list" is consistent with the name of the class and the concept of a whitelist.

From my point of view "haystack" doesn't seem to apply in the context of white/black-listing because it normally indicates a set of things that will be the target of an operation performed against them (e.g. "sort", "search" or similar). Here we don't have a haystack in that sense (except behind the scenes): we have a list of elements whose presence determine if something will be allowed through or not.

Should you not share my reasoning then I'll have no problem changing it to "haystack", just confirm and I'll do it.