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.

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.

feat(plugins): began work on supporting having plugins outside grafana, for example in grafana data dir, next step is to be able to easily specify what plugins you waant to install

override null point mode