Add influx group by

### New Feature
Ability to group results from Influxdb by arbitrary columns (e.g. host.)

Provide UI and raw query support to group influxDB results by arbitrary columns and draw each value of the group as a separate line on the graph.

![image](https://cloud.githubusercontent.com/assets/4387/3071403/15dfb5da-e2b7-11e3-9b08-2be6223f001d.png)