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.
netmhc2pan_version
the NetMHCIIpan version,
for example 3.2.
Use get_default_netmhc2pan_version to get the default
NetMHCIIpan version