Add an OpenTSDB datasource.

This adds support for querying OpenTSDB for metric data.
InfluxDB Filters: added function to generate filter list.
InfluxDB Filters: added filter to queries.
url decode metric names #327
Proof of concept of multiple groups using "host"

Initial test to make sure this plan works using a predefined alternate
group by. Now to actually figure this out based on the query and add
some UI for it.
Parse additional group by columns from a raw query

This needs some further polishing but now parse out additional group by
columns from a raw query, although it really only supports one
additional column.
Fix single line naming
Hookup additional group by into UI

Allow additional group by fields to be specified without writing a full
on influx query by hand.
Fix typos in condition names
Cleanup the influx query parsing
Add tooltip messages to icons in query editor.
Cleanup from jshint
Check for negative return
fixed issue with influxdb datasource introduced in recent filterSrv refactoring
influxdb:difference feature

Add support for the difference query from InfluxDB
Fix line length
added css concat task
trying to get css, and js build file revisioning working
Merge pull request #455 from casa87/patch-1

influxdb:difference feature
Merge branch 'master' of github.com:grafana/grafana