[ic] Clear user session after checkout

[Bob Puff]

> You could log the user out using [userdb function=logout clear=1],
> which would clear all of the user's information from the session.
> There's also the [userdb function=logout clear_session=1] usage,
> which will force an entirely new session to be created.

Most excellent, thank you sir!  I put that at the end of etc/receipt.html, and it works 
nicely.  It does print a "1" on the screen, but they can deal with that.

> See here:
> 
>     http://www.interchange.rtfm.info/icdocs/Interchange_user_database.html#logout
> 
> I should ask why a single user would want to enter lots of orders
> with different shipping and billing information, but I suspect that
> you're going to tell me that the user is some sort of administrator or
> agent.

Eggzaktly! :-) They take phone orders.