BAC-266: Memory limit exceeded: /wikia.php?controller=Lightbox&method=getMediaDetail

``WikiaFileHelper::getMediaDetail`` gets the list of articles that have given image embedded. This list is not limited. It will run out of memory for commonly used images on big wikis.

```
$ grep "Allowed memory size of " php.1 | grep getMediaDetail | wc -l
270
```

@themech @federico-lox