Fixed some broken HTML.

Validated HTTP responses

Simplified some control flow.

fix(elasticsearch): made interval template variable appear in group by time interval dropdown, fixes #3241

Return correct updated+created timestamps to frontend

Fixed created & updated columns update in dashboard table

feat(elasticsearch): a lot of work to support aggregation queries without date_histogram, queries that return metric aggregations now work with the table panel (json data type), #3219

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.