Added correct serialization to the ParameterNamespace class with a mixin
of the class ParameterNamespaceMixIn. The mixin is a official feature of
Jackson, whenever it's not possible to modify the serialized class with
other Jackson annotations.

The test with the MEC namespace now works great!

Change-Id: I5918640f3dfbb29e2824634b767fb9beb6f599ed
Signed-off-by: NeevoLima <peter.merkert@gmx.de>