add note on custom error msg container

set new value in conf
to allow control of suffix used in container Id that will hold the error message for the specific input element

   i.e. form input named "profilephoto" has a separate container that will hold a validation error message.
   that container  has an :id: = profilephoto_errMsgContainer
   the suffix "errMsgContainer" is a user configurable property

change function name to better describe its purpose