mgmt: Add tables.network_region section in config file to populate NetworkRegionTable

refs: #3159

Change-Id: If049eea2baf64a22abc9437d3ec117dd0d27bbab
diff --git a/daemon/table/network-region-table.hpp b/daemon/table/network-region-table.hpp
index 499c356..2a423a7 100644
--- a/daemon/table/network-region-table.hpp
+++ b/daemon/table/network-region-table.hpp
@@ -33,6 +33,9 @@
 /** \brief stores a collection of producer region names
  *
  *  This table is used in forwarding to process Interests with Link objects.
+ *
+ *  NetworkRegionTable exposes a set-like API, including methods `insert`, `clear`,
+ *  `find`, `size`, `begin`, and `end`.
  */
 class NetworkRegionTable : public std::set<Name>
 {