add KidsFirst hub as a default hub
add KidsFirst hub as a default hub

ucscXena/ucsc-xena-client,acthp/ucsc-xena-client,acthp/ucsc-xena-client,acthp/ucsc-xena-client,ucscXena/ucsc-xena-client,ucscXena/ucsc-xena-client,ucscXena/ucsc-xena-client,ucscXena/ucsc-xena-client