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/test/native/cpp/frc2/command/NotifierCommandTest.cpp

@@ -0,0 +1,30 @@
+/*----------------------------------------------------------------------------*/
+/* 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 "CommandTestBase.h"
+#include "frc2/command/NotifierCommand.h"
+
+using namespace frc2;
+class NotifierCommandTest : public CommandTestBase {};
+
+#ifdef __APPLE__
+TEST_F(NotifierCommandTest, DISABLED_NotifierCommandScheduleTest) {
+#else
+TEST_F(NotifierCommandTest, NotifierCommandScheduleTest) {
+#endif
+  CommandScheduler scheduler = GetScheduler();
+
+  int counter = 0;
+
+  NotifierCommand command([&counter] { counter++; }, 0.01_s, {});
+
+  scheduler.Schedule(&command);
+  std::this_thread::sleep_for(std::chrono::milliseconds(250));
+  scheduler.Cancel(&command);
+
+  EXPECT_NEAR(.01 * counter, .25, .025);
+}