Added some convenience functions
Added some convenience functions

Added a few useful functions for various convenient outputs. These include a few functions that can estimate a Sersic index value from a measure of the concentration (taken from profoundProFound( ) segmentation stats).
Also, a function to calculate the total chi squared residual between the data image and the model image has been added. The write_output( ) function has now been modified to include both the chisq value as well as the elapsed time into the Output.csv file for each optimisation run.
AstroRobin/xGASS-decomposition,AstroRobin/xGASS-decomposition