Use user display name in circle page

Use user's display name, rather than their user name, on the page for
editing circle membership.  This isn't the display name according to the
profile page; it means that for Dreamwidth users, their username appears
in the title, but for OpenID users, rather than "ext_{number}"
appearing, their OpenID URL appears.

Fixes #1608.

views/circle/individual-edit.tt

@@ -10,7 +10,7 @@ the same terms as Perl itself.  For a copy of the license, please reference
 'perldoc perlartistic' or 'perldoc perlgpl'.
 %]
 
-[%- sections.windowtitle = ".title" | ml( user => u.username ) -%]
+[%- sections.windowtitle = ".title" | ml( user => u.display_name ) -%]
 [%- sections.title = '.title' | ml ( user => u.ljuser_display( head_size = "24x24" ) ) -%]
 [%- CALL dw.active_resource_group( "foundation" ) -%]