Add warning about choosing unique last word in class name to avoid conflicts and enable correct save button behaviour

Add warning about choosing unique last word in class name to avoid conflicts. Not sure this is the best place to document this, but seems the most relevant. Probably not a big deal for most of these words, but I can imagine I'm not the only one who would use CRM_MyExtension_Form_Settings (Info and Settings) or Event (used for Tell a Friend).

Also, more importantly, it turns out that the class name must match the path in order for save to work correctly (to redirect back to the same page).