Change skip_user_confirmation_email to send_user_confirmation_email

CHANGELOG

app/controllers/admin/application_settings_controller.rb

app/models/user.rb

app/views/admin/application_settings/_form.html.haml

...09_add_send_confirmation_email_to_application_settings.rb

...09_add_skip_confirmation_email_to_application_settings.rb

spec/controllers/registrations_controller_spec.rb

spec/features/signup_spec.rb

spec/models/user_spec.rb