Add some additional tests to validate handling null values behaves as
expected.
Test basic message property for AmqpJmsMessageFacade.  Fix up a few null
check issues, and use the AmqpJms facade types as covariant return types
from the copy methods to make testing easier, no casts needed.
Additional check to filter out replyToGroupId if its an empty string
also.
Test for number of message properties and fix copy incorrectly mapping
replyTo into the replyToGroupId feild.
Start testing the AmqpJmsMessagePropertIntercepter.  Work in progress as
the object message type bits are complete.