Remove the <Z> from JmsMatsFactory

[stolsvik]

The type here is just a "transfer type" between the MatsTrace and the MatsSerializer, which are intrinsically linked, and should not be exposed to the user.

Object is probably the better type here: JmsMatsFactory just passes an Object (serialized STO or DTO) from the MatsTrace to the MatsSerializer, and it will have to cast it to whatever it really is.

Another option is possibly a "Holder" - but I currently don't see how that would work with the MatsTraceFieldImpl, which needs an actual type for the STO and DTO serialized fields.