enum Aggregation

The aggregation method for a Measurement Type.

References from:: MeasurementType;

`2`	`SUM` Aggregation method = SUM.
`3`	`AVG` Aggregation method = AVG.
`4`	`MIN` Aggregation method = MIN.
`5`	`MAX` Aggregation method = MAX.
`6`	`LAST_UPDATE` Aggregation method = LAST_UPDATE.

enum Aggregation