same behaviour for Page->getAttribute like UserInfo->getAttribute

as suggested by @aghouseh in this pull request https://github.com/concrete5/concrete5/pull/1215.

Page->getAttribute has an optional second parameter like UserInfo->getAttribute

When working with a date attribute, we can use this to get the proper output value:

```php
echo $p->getAttribute('date_attribute_handle', 'display');
```

I hope that more people will start using the display output which makes it possible to format dates.