Set the devise secret in all environments

To prevent a deprecation warning from devise.  We override this value in deployed environments.
See heartcombo/devise#5644

config/settings.yml

@@ -20,6 +20,7 @@ ANALYTICS_DEBUG: true
 PAGINATION_THRESHOLD: 250
 EMAIL_THRESHOLD: 5
 GENERATE_SITEMAP: true
+DEVISE_SECRET_KEY: <%= Rails.application.secret_key_base %>
 DISABLE_SESSIONS: false
 THROTTLE_TRAFFIC: false
 OCLC: