This change removes the script_type parameter form the Scripted Metric Aggregation and adds support for _file and _id suffixes to the init_script, map_script, combine_script and reduce_script parameters to make defining the source of the script consistent with the other APIs which use the ScriptService
Changes the name of the field in the scripted metrics aggregation from 'aggregation' to 'value' to be more in line with the other metrics aggregations like 'avg'