Ensemble statistics: Remove zero values for derived summary vectors when calculated statistics

[hhgs]

To calculate the statistical curves for ensembles (P10/50/90/Mean), ResInsight includes all realizations at all time steps, regardless of whether the field/well is producing or shut. That makes sense for volume-related parameters such as production rate, total production, in-place volumes, recovery factor.

For parameters like derived parameters like water-cut (WCT), gas-oil-ratio (GOR) and well productivity index (PI), zeros caused by field/group/well being shut should not be included when calculating statistics.

[magnesj]

Add an option to RimEnsembleStatistics called m_includeZeroValues, default on. If this is toggled off, curve values with zero is excluded from the statistics computation in RimEnsembleStatisticsCase::calculate