Support for Wikidata URIs

[ram-g-athreya]

Presently we ground questions to only DBpedia URIs. Try to extend this to Wikidata URIs.

[aliiakbarkhan]

Hi @ram-g-athreya, hope you are doing well.
I have just added a PR implementing this upgrade. As a beginner, I tried to do it as best as I could.

Thank you.