Ignore nulls unless 'null as zero' for series.stats.avg

(prometheus) support null point mode

(cloudwatch) fix null point mode

[prometheus] Fix step calibration

Duplicate button for template variables

The step interval is (correctly) being converted to seconds, but the
unit of measure suffixed onto the end is preventing the subsequent
step calibration. Because the query upstream defaults to seconds as
the unit of measure, the suffix can simply be removed and everything
works as intended.

patchset 01: Also fix the spec.

specify date format in elastic search query

Fix recommended graphite version for better performance

There is no 0.9.13 graphite release, only 0.9.14.

override null point mode

(cloudwatch) support null point mode

(cloudwatch) support ECS suggestion

/api/admin/users returns user ID in JSON response

Made opentsdb query editor consistent and tags are editable now

fix(http api): correct return status code for /api/datasources/:id so it eturns 404 when not found, fixes #3217