#29: person registering the group can now kick in extra

I'm still leaving donations disabled for dealers, which I have mixed feelings about; we can talk about it if people feel differently.  (This would need to be tested separately although that's not the reason I'm leaving it disabled for them.)

My main objection is that our dealer application process is super-competitive, and people might feel like they were being pressured to kick in extra to assure that they'd get a spot.  "Pretty nice dealer application you've got there, would be a shame if we didn't accept it because you didn't kick in extra."  I'm not personally comfortable with that; I'd be totally fine with an open auction or something where it was clear what the rules are, but I'd hate to have an implied (even if only unintentionally implied) pressure like that.