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.
@pauldix the periods will also have correct values for downsampled shards right? we could automatically set this based on what the CQ group by time says.  you also mentioned somewhere else that because we can have different steps (oh btw, i prefer `step` over `period`) as metadata in different shards, we can keep the series names the same, right? that seems nice to me, but some people didn't like it when i suggested this back in februari (https://groups.google.com/forum/#!topic/influxdb/Km9jzwCXhPc)