added MemberAttributeConfig serialization via XML

1. hazelcast-spring serializaion (see hazelcast-spring-3.3.xsd)
2. hazelcast serialization (see hazelcast-config-3.3.xsd)

see the discussion about this feature: https://groups.google.com/forum/#!searchin/hazelcast/memberattribute/hazelcast/H4uN1aSszjY/C6QP_1KQvdQJ