Fixed a bug in date_histogram aggregation parsing

 - pre_zone_adjust_large_interval was not parsed properly
 - added tests for pre_zone and pre_zone_adjust_large_interval
 - changed DateHistogram#getBucketByKey(String) to support date formats (next to numeric strings)
 - added randomized testing for fetching the bucket by key in date_histogram tests
 - added missing "format" support for the DateHistogramBuilder

 Closes #5375