Http api

First pass wire up of (most) HTTP endpoints but without authentication.
@otoolep we could prevent the JSON encoder / decoder from looking at this field using a tag but I thought we might need it internally in InfluxDB so I just decided to blank it out at this endpoint where I know we don't want to send it.  There is another possible way...make the `Hash` field a `*string` and then set it to `nil` but I didn't see any benefit to that.