Support a configuration-driven whitelist of ids that can be teed off for ucsf participants

@kentquirk Can you have a look at this.  I just verified that it appears to be working so I think I'm ready to call it done.
How about also discarding whitespace in the elements of the string so that it's easier to manage the environment? I know I'd be inclined to split it up with newlines, and it's almost impossible for me to NOT put a space after a comma.