Implemented two new configuration parameters for the computation of the final Q-, U-, I_Q- and I_U-images

• Implemented two new configuration parameters (combination_method_polarization and combination_method_intensity) for the computation of the final Q-, U-, I_Q- and I_U-images. The Q- and U-images can now be computed using least squares (as was previously the only option), the median and the trimmed mean. The I_Q- and I_U-images can be computed from the mean (as was previously the only option), the median and the trimmed mean
• Old configuration files that do not have these parameters can still be used: IRDAP automatically uses the default least squares and mean options if these new configuration parameters are missing from the configuration file
• Some minor additional improvements