Add definition for _key, _to and _from, sort reserved words in aggregation_metric.cc
Add definition for _key, _to and _from, sort reserved words in aggregation_metric.cc

Kronuz/Xapiand,Kronuz/Xapiand,Kronuz/Xapiand,Kronuz/Xapiand,Kronuz/Xapiand,Kronuz/Xapiand