Fix "Send me reset password instructions" [#736901]

We added "display_name" to all Objects in 00_core_extensions.rb

adding this to all objects broke action mailer's duck typing:
see the lines in lib/mail on github: http://bit.ly/17dc8kO

From: https://www.pivotaltracker.com/projects/736901#
Forgot my password.

Was on this page:
http://authoring.concord.org/users/password/new

Entered my email address.

Clicked "Send me reset password instructions"  button.

Rails displayed: "We're sorry, but something went wrong." in red -- this is normally what appears when there is a 500 Server Error