KapuaMessage and KapuaPayload marshalling error

[muros-ct]

While writing unit tests for message module I discovered two issues with marshaling Kapua objects to XML.
Problem seems to be with marshalling of byte[] elements.

Tests that present the issue are in kapua-message module:

• org.eclipse.kapua.message.internal.KapuaMessageTest.marshallMessage()
• org.eclipse.kapua.message.internal.KapuaPayloadTest.marshalPayload()

Both tests are now ignored by message that marshalling is not working.
Please un-ignore tests to see exception message:

java.lang.NoClassDefFoundError: javax/mail/internet/MimeMultipart

Issue might be related to problem that XML annotations are on classes and not on Interfaces, which is the practice for other data objects.