Match another field(or entity property)

This is a powerful validator that could be used on many case. it support multiple arguments for "another field":
include: entity_type, field_name, bundle, column, is_property. Here is some example when you config the validation rule:
for example,
1, make sure the value entered is a valid username,
entity_type=user&column=name&is_property=TRUE

2,validate against Article's title:
entity_type=node&bundle=article&column=title&is_property=TRUE

3,validate against User's realname field:
entity_type=user&field_name=field_realname&column=value

This validator leverages the EntityFieldQuery, some entity does not support bundle in entityCondition, you should make it correctly by yourself.