Mostly code cleanup: trying to find more logical names for the buffering code in BufferedIOHandler, more modularity in InterpolationAlgorithms. Since when computing a variogram from time series it is possible to end up with significantly lower values than usual that lead the krigging in a totally wrong direction (should the variogram be normalized? Is it linked with the stationarity hypothesis?), now the empirical variogram is used instead of the full time series.