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/measurements.cpp b/daemon/table/measurements.cpp
index c939b72..d93cc91 100644
--- a/daemon/table/measurements.cpp
+++ b/daemon/table/measurements.cpp
@@ -45,7 +45,7 @@
     return *entry;
   }
 
-  nte.setMeasurementsEntry(make_unique<Entry>(nte.getPrefix()));
+  nte.setMeasurementsEntry(make_unique<Entry>(nte.getName()));
   ++m_nItems;
   entry = nte.getMeasurementsEntry();
 
@@ -165,7 +165,7 @@
   BOOST_ASSERT(nte != nullptr);
 
   nte->setMeasurementsEntry(nullptr);
-  m_nameTree.eraseEntryIfEmpty(nte);
+  m_nameTree.eraseIfEmpty(nte.get());
   --m_nItems;
 }