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.
This makes sense to me. However, our system will need some way -- or at least an answer -- about how to deal with the case where a user *inadvertently* writes a string version of, say, a double, which locks down the type. He then realises his mistake, and tries to correct it by writing doubles (he fixes his code). How will he do this? Will he able to? I've come across this type of problem before.

Not something we have to address now, but it is a real practical problem.