Extend `MeasurementObservation` to accept `aggregation_period`, `reporting_schedule`, and `period_end_dow`

[cdc-mitzimorris]

Once issue #789 has been implemented for CountObservation and subclasses, we will need to change MeasurementObservation to match.

Implementation of #789 will add helper methods on the BaseObservationProcess so that all code and logic is reusable.