The Fit1D class constructor can now read a fit model name as a string. This was necessary for parsing a user input coming from io.ini. 

The ordinary kriging interpolation algorithm is now active. It is far from perfect (the variogram is computed in a very cheap way that contributes to make it very fragile), but it is time for the first users to start playing with it. The variogram model to use can be provided as an optional argument and in case of fit failure, an appropriate error message is given (but no fallback mechanism exists). The next step will be to compute the variogram on time series, which should produce more reliable data sets for fitting the variogram model on.

Some error messages have been improved in the matrix class.