Add support for Symfony GreaterThan Constraint

manual test case:
add a GreaterThan constraint to field_test_int, set value = 10, save it.

if populate field_test_int 5, get an error message.

if populate field_test_int 10, get an error message.

if populate field_test_int 20, no error message.

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