Return more meta data & restructure reponse format

[tholor]

Let's return a bit more information from the Finder / in the API and adjust the response format:

• offsets in the original doc (needed for feedback endpoint)
• custom meta data (whatever is available in elasticsearch and is not excluded via excluded_meta_datain the ElasticsearchDocumentStore
• move name into the meta field

{
    "results": [
        {
            "question": "Why did revenue increase?",
            "answers": [
                {
                    "answer": "Total revenue for the first quarter of 2017 was approximately $1,437,000,000",
                    "score": 3.589367151260376,
                    "probability": 0.6103231806375512,
                    "context": "<Some context>",
                    "offset_start": 212,
                    "offset_end": 288,
                    "offset_start_in_doc": 5674,
                    "offset_end_in_doc": 5750,
                    "document_id": "cqjbqnABdLrIEs4cBtTh",
                    "meta": {
                        "quarter": "Q1",
                        "year": "2017",
                        "company": "<Some Name>",
                        "name": "<Some File Name>.txt"
                    }
                },