Add an OpenTSDB datasource.

This adds support for querying OpenTSDB for metric data.
Add support for multiple hosts (with retries) and raw queries.
version bump to 1.5.3
updated changelog
Added rounding for graphites from and to time range filters
  for very short absolute ranges (Fixes #320)
Merge branch 'influxdb-updates' of github.com:influxdb/grafana into influxdb-influxdb-updates
influxdb editor: rawquery text input, changed from fixed pixel width to span10 class
added support to coustom where conditions
Merge branch 'master' into feature/influxdb-add-where-conditions

Conflicts:
	src/app/partials/influxdb/editor.html
	src/app/services/influxdb/influxdbDatasource.js
Added where condiction operators
Added conditions management
Added labels per series management
better variable naming
removed unrequired variable (error on merge from master)
Increased resolution for graphite datapoints (maxDataPoints), now equal to panel pixel width. (Closes #5)
Merge branch 'feature/influxdb-add-where-conditions' of github.com:mavimo/grafana into mavimo-feature/influxdb-add-where-conditions
Review and small refactoring of PR #331
Closes #333, New version availability check will now checks http://grafanarel.s3.amazonaws.com/latest.json if there is a new version. And the link now points to http://grafana.org/download
began work on unsaved changes warning when changing dashboard, Issue #324
New config setting for graphite datasource to control if json render request is POST or GET (Closes #345)