TRUNK-5136 Add custom hamcrest matcher HasFieldErrors
* add a custom hamcrest matcher HasFieldErrors which enables
assertThat(errors, hasFieldError());
assertThat(errors, hasFieldError("text"));
assertThat(errors, hasFieldError("text", "error.null"));
* matcher has factories which enables the above after static imports of
the matcher
* show use of matcher in PersonNameValidatorTest
