Because even if it doesn't make a difference in practice, it is
technically more correct to call static methods statically. It
also better advertise that those methods can be used from any context.
Settings: deleted libxml_disable_entity_loader() calls since they're not necessary.
Prevent setLibXmlLoaderOptions() and getLibXmlLoaderOptions() to call the libxml_disable_entity_loader() function which alter the global state of libxml.
See the discussion here https://github.com/PHPOffice/PhpSpreadsheet/issues/74
Adrien Crivelli