Applied small optimization

reCaptcha answers with `ERROR_INVALID_COOKIE`, if javascript is disabled and the given answer within the fallback is wrong/malformed. In this case it's recommended to throw a `UserInputException` instead of a `SystemException`.
Moved 3rdpartyFields to a better position
json_decode() will raise a warning on invalid input (PHP 5.6)
This doesn't belong here
Merge pull request #1740 from SoftCreatR/patch-1

reCaptcha optimization
Merge pull request #1754 from SoftCreatR/patch-9

Move 3rdpartyFields to a better position
Merge branch '2.0'