Improved wording of Model::invalidFields()

Inspired by
http://book.cakephp.org/2.0/en/models/data-validation/validating-data-from-the-controller.html#validating-data-from-the-controller
Merge pull request #1645 from ShinKenDo/patch-1

Improved wording of Model::invalidFields()
Fix wording and remove trailing spaces.
removed duplicate test case

Was exact duplicate of case starting line 692
Merge pull request #1646 from spiliot/patch-1

removed duplicate test case in CakeRequest Referer
Fix label element for attributes not matching their inputs.

Radio elements would contain ModelModelFieldValue instead of
ModelFieldValue like they should. This was caused by the fix for #3936
and lack of tests for create() + radio().

Fixes #4071