Jim Ferenczi 19cfc25873
Adds the ability to specify a format on composite date_histogram source (#28310)
This commit adds the ability to specify a date format on the `date_histogram` composite source.
If the format is defined, the key for the source is returned as a formatted date.

Closes #27923
2018-01-23 15:14:49 +01:00
..
2017-12-14 17:47:53 +01:00
2017-12-14 17:47:53 +01:00