Added _ to list of allowed characters in filename regex
Added _ to list of allowed characters in filename regex

hms-dbmi/fourfront,hms-dbmi/fourfront,4dn-dcic/fourfront,hms-dbmi/fourfront,hms-dbmi/fourfront,4dn-dcic/fourfront,4dn-dcic/fourfront,4dn-dcic/fourfront,hms-dbmi/fourfront