Add support for Symfony NotEqualTo Constraint

test case:
add a NotEqualTo constraint to field_test, set value to "abc", save it.

if populate field_test "123456", no error message.

if populate field_test "abc", get an error message

the value option support token, when using "default" validate mode.
you can insert a token : [node:field_other_test]

"Direct" validate mode does not support Drupal's token.

Automatically closed - issue fixed for 2 weeks with no activity.