Use new NetworkTables across WPILib (C++ and Java).

Also make sure table listeners stop listening in their destructors.  This
might be better handled by moving the table itself into ITableListener and
providing cleanup functionality there.

A submodule is used to pull in ntcore.

Change-Id: I3031c1a768595cf0f8754c47e15cd423e2dbcce5

wpilibc/wpilibC++Devices/src/RobotBase.cpp

@@ -15,6 +15,7 @@
 #include "HLUsageReporting.h"
 #include "Internal/HardwareHLReporting.h"
 #include "Utility.h"
+#include "networktables/NetworkTable.h"
 #include <cstring>
 #include "HAL/HAL.hpp"
 #include <cstdio>
@@ -51,6 +52,8 @@ RobotBase::RobotBase() : m_ds(DriverStation::GetInstance()) {
 
   RobotBase::setInstance(this);
 
+  NetworkTable::SetNetworkIdentity("Robot");
+
   FILE *file = nullptr;
   file = fopen("/tmp/frc_versions/FRC_Lib_Version.ini", "w");