Changed serializer to XmlContentSerializer instead
Changed serializer to XmlContentSerializer instead

of ConventionBasedSerializerOfComplexImmutableClasses in a test case, in
order to get rid of this legacy class. The point of this test case is that
AtomEntry can properly serialize and deserialize, and not so much which
serializer is used.

GreanTech/AtomEventStore,GreanTech/AtomEventStore