Experiment participant pool

[johnwdubois]

1. As a prototype, use the UCSB participant pool:

• some students (participants) are signed up to participate in certain experiments
• give the appropriate participants a link to URL where the experiment is hosted (e.g. on Firebase)

2. Use Firebase to create one or more top-level pool(s) for experimental participants

• call it ParticipantPool or just Pool
• Participants can sign up to join a specific ParticipantPool (or perhaps more than one).
• An experimenter has rights to recruit participants who have signed up (and given consent) to participate in a particular ParticipantPool, adding them to their experiment.