Preserve and present what the user understands as their login name in the

... settings Account info screen.  If the username is different than the login
name, present both.  Otherwise, just present the username.

(It may be unnecessary, from the user's point of view, to present both.
I'm not acquainted with use of blue/enterprise accounts, so don't know
whether or not the username is a totally internal detail, and/or whether it
would be useful debugging info, so I'm erring on the side of completeness.)

Fixes #276.