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.

wpilibNewCommands/src/main/native/cpp/frc2/command/ProxyScheduleCommand.cpp

@@ -0,0 +1,37 @@
+/*----------------------------------------------------------------------------*/
+/* Copyright (c) 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 "frc2/command/ProxyScheduleCommand.h"
+
+using namespace frc2;
+
+ProxyScheduleCommand::ProxyScheduleCommand(wpi::ArrayRef<Command*> toSchedule) {
+  SetInsert(m_toSchedule, toSchedule);
+}
+
+void ProxyScheduleCommand::Initialize() {
+  for (auto* command : m_toSchedule) {
+    command->Schedule();
+  }
+}
+
+void ProxyScheduleCommand::End(bool interrupted) {
+  if (interrupted) {
+    for (auto* command : m_toSchedule) {
+      command->Cancel();
+    }
+  }
+}
+
+void ProxyScheduleCommand::Execute() {
+  m_finished = true;
+  for (auto* command : m_toSchedule) {
+    m_finished &= !command->IsScheduled();
+  }
+}
+
+bool ProxyScheduleCommand::IsFinished() { return m_finished; }