Define normalized response structure

[danibishop]

We need a common structure for query responses regardless of what datasource is being used.

[josemazo]

The one you proposed looks nice to me, but the rows, the need to be key-value pairs. It would be awesome if we can also obtain the fields and the response_time in the same query with PG. And the cache field is what excites me the most.

[danibishop]

I implemented the CARTO row style (including field name) for the default response. I added some profiling values that should be revised/rethinked. For now, some elapsed times, which are specific for each data source.