Remove the code for handling images in the core #25
Description
Measurements by @alemela have shown that we can get rid of the code for handling images in the core. There are two arguments against that.
First, those images are links taken from the latest DBpedia dump, which may be months old, so it's more effective to ask images to Wikipedia, instead, when one wants to display them (images that may be more appropriate than the old ones).
Second, there are many cases in which the image is missing or wrong. So, it seems pointless to use a mechanism that fails in (@alemela correct me if I'm wrong) more than 50% of the cases.
The removal of the code should not affect the API. We should, instead, just return an empty string (or a null) in the image field in the returned vector.