Split the two command implementations into separate libraries (#2012)

This will allow us at the user code side to determine to include old commands, new commands or both.

wpilibOldCommands/src/main/native/cpp/commands/InstantCommand.cpp

@@ -0,0 +1,45 @@
+/*----------------------------------------------------------------------------*/
+/* Copyright (c) 2016-2019 FIRST. All Rights Reserved.                        */
+/* Open Source Software - may be modified and shared by FRC teams. The code   */
+/* must be accompanied by the FIRST BSD license file in the root directory of */
+/* the project.                                                               */
+/*----------------------------------------------------------------------------*/
+
+#include "frc/commands/InstantCommand.h"
+
+using namespace frc;
+
+InstantCommand::InstantCommand(const wpi::Twine& name) : Command(name) {}
+
+InstantCommand::InstantCommand(Subsystem& subsystem) : Command(subsystem) {}
+
+InstantCommand::InstantCommand(const wpi::Twine& name, Subsystem& subsystem)
+    : Command(name, subsystem) {}
+
+InstantCommand::InstantCommand(std::function<void()> func) : m_func(func) {}
+
+InstantCommand::InstantCommand(Subsystem& subsystem, std::function<void()> func)
+    : InstantCommand(subsystem) {
+  m_func = func;
+}
+
+InstantCommand::InstantCommand(const wpi::Twine& name,
+                               std::function<void()> func)
+    : InstantCommand(name) {
+  m_func = func;
+}
+
+InstantCommand::InstantCommand(const wpi::Twine& name, Subsystem& subsystem,
+                               std::function<void()> func)
+    : InstantCommand(name, subsystem) {
+  m_func = func;
+}
+
+void InstantCommand::_Initialize() {
+  Command::_Initialize();
+  if (m_func) {
+    m_func();
+  }
+}
+
+bool InstantCommand::IsFinished() { return true; }