According to the documentation, `AnyMetaDef.metaType` should default to `"string"`. However, such default value doesn't exist. This causes `AnyMetaDef.metaValues` not respected when `AnyMetaDef.metaType` is not presented.

Besides annotations, xml configuration have similar problem. `hibernate-mapping-3.0.dtd` and `hibernate-mapping-4.0.xsd` says `<any/>`'s `meta-type` defaults to `"string"`, but it's not.