Fib::removeNextHopFromAllEntries automatically deletes fib::Entry
if the last nexthop record is being removed.
refs #1341
Change-Id: I36d42fe8f9fc8f03d194f845020aff408cd70488
Also, this commit imports used classes from ::ndn namespace (from
NDN-CPP library) directly to ::nfd namespace.
refs: #1163
Change-Id: I9cc9d72e00af495b4ed0c84e6d418a7c9ba986cb