the folder (to be) used by NetMHCIIpan.
From this location, a subfolder for NetMHCIIpan is created.
Use get_default_netmhc2pan_folder to see the location
of the default NetMHCIIpan folder.
Use get_default_netmhc2pan_subfolder to see the location
of the default NetMHCIIpan subfolder.