Reporting namespace

As we don't consider the reporting interface well defined and unstable I propose we move the following classes into the `Reporting` namespace. Also mark this module as private - use at own risk.
* `Aggregate`
* `AggregateArray`
* `DayRange`
* `HourRange`
* `LineAggregate`
* `MonthRange`
* `TimeRange`
* `TimeRangeArray`
* `WeekRange`
* `YearRange`