Update post-install scripts (win, macos, linux) to add faust data dir in...

Update post-install scripts (win, macos, linux) to add faust data dir in matlab path and to secure further the update of th e path for matlab.

Each existing startup user's script are updated with addpath.
addpath is only executed if matfaust.version is not found in matlab path.
matlabrc calls startup to be sure (in case of not updated matlab path cache).
https://fr.mathworks.com/help/matlab/matlab_env/toolbox-path-caching-in-the-matlab-program.html
https://fr.mathworks.com/help/matlab/ref/rehash.html
https://fr.mathworks.com/help/matlab/ref/matlabrc.html
https://fr.mathworks.com/help/matlab/ref/startup.html