Bring general_settings_helper from spree_backend

app/helpers/spree/admin/general_settings_helper.rb

@@ -0,0 +1,13 @@
+module Spree
+  module Admin
+    module GeneralSettingsHelper
+      def currency_options
+        currencies = ::Money::Currency.table.map do |code, details|
+          iso = details[:iso_code]
+          [iso, "#{details[:name]} (#{iso})"]
+        end
+        options_from_collection_for_select(currencies, :first, :last, Spree::Config[:currency])
+      end
+    end
+  end
+end