Fitting code contribution: SR_LUMC Matlab code for IVIM, DTI, and IVIM-DTI fitting

[s-rauh]

Fitting code contribution in src/original/fitting. The code contains Matlab fitting routines for IVIM, IVIM-DTI, and DTI.

[s-rauh]

Thanks for looking into the code. I adjusted a few things:

Models: The folder "models/" including the ivimfun, dtifun etc was indeed missing, thanks for spotting this. "models" appears in gitignore (which I missed). I renamed the folder and added it.

1. remove_zeros.m: I adjusted the code accordingly
2. fit_ivim.m option 'segmented': I corrected the data selection for this option
3. norm_diffdata.m: the normalization is performed before b-value scaling, so it should not be a problem. However, as the differentiation was redundant, I adjusted the code to always use normalization to the minimum b-value:
   if min(bval) > 0
   fprintf('No b = 0 data provided. Normalize to minimum b-value data: %.2f s/mm². \n',...
   min(bval))
   else
   fprintf('Normalize data to b = %.2f data. \n', min(bval))
   end

mS0 = mean(data((bval == min(bval)),:), 1);

normalized = data ./ mS0;
normalized(isnan(normalized)) = 0;

[s-rauh]

I added a setup.m file to add the path before using the code and added a statement in the readme.
I also added a check for non-finite values in the FA map in calc_dti_parameters.m