Add extra_modules_script parameter, like RStudio app

[elelaysh]

It is simply the path to a shell file that will be sourced in the launch script

[elelaysh]

Be sure to include the notebook module in the module/virtualenv you load this way, because if only jupyter is present, the jupyter-notebook command from the default path could be used, resulting in the default kernel being the one from the default path, not the module you loaded.