NDN Packet Format v0.3 is introducing a new Interest packet format. Compared to v0.2.1 packet format, the differences are: * Optional **CanBePrefix** and **MustBeFresh** elements are added after Name. * **Nonce** becomes optional. * **ForwardingHint** is moved before Nonce and InterestLifetime. * Optional **HopLimit** and **Parameters** elements are added after InterestLifetime. This issue changes `ndn::Interest` class to recognize v0.3 format, and interpret it as into v0.2 semantics. Encoder continues to emit v0.2 format, and remains unchanged under this issue. As part of [[nfd:Packet03Transition]], this It is an interim step for a forwarder or application to receive Interest v0.3 without any changes.