DDSJAVA — RxO QoS Policies should be Comparable (idem for QoS)

Some of the DDS QoS Policies are Request vs. Offered in the sense that
the value of matching policies on communicating entities have to satisfy a
specific ordering relationship. Specifically, the policy set on the receiving side
should always be less or equal than the analogous QoS Policy on the
sending side. As a result there is a natural total ordering for RxO Policies
which is not currently captured nor reflected in the API.

As a consequence also QoS should be defining a total order.

[Resolution]
Ensure that all RxO Policies implement the Comparable interface. This is
pretty logical as for this QoS Policies it has to be established
a total order.

Let QoS classes also implement a comparable interface.

Define an interface RequestedOffered; all QoS policy types that require requested/offered compatibility extend this interface. The interface has one method, requestedOfferedContract, which returns a Comparable object. That objects compares the policy against another instance of the policy based on the requested/offered compatibility rule(s) for that policy type.