Pearson correlation single timeseries broadcasting

[JanisGailis]

Currently Pearson correlation supports correlation calculation between datasets of the same shape. E.g., if two lat/lon/time datasets are provided, they must be of the same shape and then correlation will be calculated for each spatial point against the corresponding spatial point in the other dataset.

If 1D datasets of 'time' dimension are provided, then the correlation calculation will produce a single correlation coefficient for the given pair.

However, in Use Case 6 one should be able to produce a correlation map where each spatial point in a given region is correlated against the same ENSO Index timeseries. E.g., the ENSO index timeseries should be broadcast against a lat/lon/time dataset, and produce a map of correlation coefficients.