Added a setter method for label_field_id in content_types.rb model. Should resolve issue where label_field_name was not being updated properly through the UI. Fix for issue #398.

app/models/locomotive/content_type.rb

@@ -83,6 +83,13 @@ module Locomotive
     def class_name_to_content_type(class_name)
       self.class.class_name_to_content_type(class_name, self.site)
     end
+    
+    def label_field_id=(value)
+      # update the label_field_name if the label_field_id is changed
+      new_label_field_name = self.entries_custom_fields.find(value).name rescue nil
+      self.label_field_name = new_label_field_name
+      super(value)
+    end
 
     def label_field_name=(value)
       # mandatory if we allow the API to set the label field name without an id of the field