Update addFSDA2path.m

After creating the toolbox folder and moving the first source code folder into the /toolbox leaves the toolbox repository in a state of despair.

This difficulty can be temporarily fixed by using the addFSDA2pathe.m. This script can be used to add the required folder to MATLAB so that the FSDA toolbox works properly. Modify this script whenever a toolbox folder is moved into /toolbox.