"Nickname" when adding new users is confusing

[markjaquith]

When you add WP users from within WP, the username is called "Nickname." When users self-register, it is properly called "Username." It isn't clear that "Nickname" is actually a username. People are inclined to put a long, capitalized, even spaced name in "Nickname" because they don't realize that this is the username they're going to have to remember and type verbatim in order to be able to log in.

Recommend changing this to "Username" to be consistent and clear.

use "Username" instead of "Nickname"

Lovely.

#2940 has a better patch for this