table: delete deprecated functions in NameTree

NameTree::eraseEntryIfEmpty is renamed to eraseIfEmpty;
the deprecated overload that accepts shared_ptr<name_tree::Entry> is deleted.
name_tree::Entry::getPrefix is deleted in favor of getName.

This commit also improves Doxygen in NameTree class.

refs #3687

Change-Id: Ia98ca676ce6d3bc7b2e97328adccac911c8167d7
diff --git a/daemon/table/fib.cpp b/daemon/table/fib.cpp
index 890bbbe..d18ce94 100644
--- a/daemon/table/fib.cpp
+++ b/daemon/table/fib.cpp
@@ -136,7 +136,7 @@
 
   nte->setFibEntry(nullptr);
   if (canDeleteNte) {
-    m_nameTree.eraseEntryIfEmpty(nte);
+    m_nameTree.eraseIfEmpty(nte.get());
   }
   --m_nItems;
 }