Show tabs for existing custom field types only and adds a view for choosing the type when adding a new custom field.

git-svn-id: http://svn.redmine.org/redmine/trunk@12849 e93f8b46-1217-0410-a6f0-8f06a7374b81

app/controllers/custom_fields_controller.rb

@@ -77,7 +77,7 @@ class CustomFieldsController < ApplicationController
   def build_new_custom_field
     @custom_field = CustomField.new_subclass_instance(params[:type], params[:custom_field])
     if @custom_field.nil?
-      render_404
+      render :action => 'select_type'
     end
   end