Refactor api

Here are some of my ideas around refactoring how InfluxDB's API works. The key learning here is that people have been using string columns like tags and it leads to bad performance.

My goal here is to make that the default and to expose an API that is more purpose built around the metrics/time series use case as opposed to the more general purpose SQL.

Please comment on the individual lines of [influx_api_v2.md](https://github.com/influxdb/influxdb/blob/refactor-api/influx_api_v2.md) for focused feedback. Or leave comments in the thread for more general thoughts.

I'm also very interested in hearing about specific use cases. Have I captured everything here? What have I left out? I know this can't encompass everything, but my hope is that it creates a clean foundation that we can easily expand upon.

@jvshahid, @toddboom, @benbjohnson, @dgnorton, @otoolep: please to review.
I had multiple people mention to me when I presented some of these ideas that they thought hierarchy was a good idea. I think it was with respect to building graphs and stuff like that. Basically the idea of a drill down. But of course, you can drill down with a flat tag structure too i.e. faceted search.

@torkelo can you chime in here on why a hierarchy might be desirable? I'm also beginning to doubt that it's a good idea.