[API] Return a list of answers for every question in 'api/v1/questions/'

[albertinisg]

As found in several questions like:

How do I get answers by using the Rest API?
Web API for answers export?
Adding Answer Functionality to the API

There's no way to retrieve the answers through the API. I've tried to find the functionality which is not avilable, but I've found a PR with a similar approach:

#334

As modern API's models returns all the information in the same entity (question), why not to retrieve all the answers in a list called 'answers' instead just 'answer_ids'? It should be an easy change. Would you accept a PR for that?

Best!