add pcawg hub to default and enabled hub list. For public release Feb 5th.
add pcawg hub to default and enabled hub list. For public release Feb 5th.

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