Extract ProcedureTimeExtrema to separate class
Add first/last timestamp column name constants
Add method to query procedure time extrema from series first/last time stamp
Get from procedure time extrema from series first/last timestamp if available. Else use the old implementation.
Merge pull request #130 from CarstenHollmann/feature/use_series_first_last_timestamp_if_available_for_procedure_timeextrema

Use series first last timestamp if available for procedure time extrema