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/cleanup.cpp b/daemon/table/cleanup.cpp
index 0ba0725..8317099 100644
--- a/daemon/table/cleanup.cpp
+++ b/daemon/table/cleanup.cpp
@@ -44,7 +44,7 @@
     }
 
     if (nte.getFibEntry() == nullptr && !nte.hasPitEntries()) {
-      maybeEmptyNtes.emplace(nte.getPrefix().size(), const_pointer_cast<name_tree::Entry>(nte.shared_from_this()));
+      maybeEmptyNtes.emplace(nte.getName().size(), const_pointer_cast<name_tree::Entry>(nte.shared_from_this()));
     }
   }
 
@@ -53,7 +53,7 @@
     shared_ptr<name_tree::Entry> nte = i->second.lock();
     // nte may have been erased when its last child is erased
     if (nte != nullptr) {
-      nt.eraseEntryIfEmpty(nte);
+      nt.eraseIfEmpty(nte.get());
     }
   }
 }