unsetAll(), nullifyEmptyStrings

unsetAll is a convenience method that will remove all elements specified by the `$keys` array.

nullifyWhiteSpace will convert all strings containing only whitespace to null. Usefull for db inserts when you want to insert null and not an empty string.
This function could also be implemented as:
```php
$array = array_diff_key($array, array_flip($keys));
```

I definitely agree that `unsetAll` is a bit nicer, but does it add enough value to be included here?