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/include/frc2/command/InstantCommand.h

@@ -0,0 +1,48 @@
+/*----------------------------------------------------------------------------*/
+/* 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.                                                               */
+/*----------------------------------------------------------------------------*/
+
+#pragma once
+
+#include "CommandBase.h"
+#include "CommandHelper.h"
+
+namespace frc2 {
+/**
+ * A Command that runs instantly; it will initialize, execute once, and end on
+ * the same iteration of the scheduler.  Users can either pass in a Runnable and
+ * a set of requirements, or else subclass this command if desired.
+ */
+class InstantCommand : public CommandHelper<CommandBase, InstantCommand> {
+ public:
+  /**
+   * Creates a new InstantCommand that runs the given Runnable with the given
+   * requirements.
+   *
+   * @param toRun        the Runnable to run
+   * @param requirements the subsystems required by this command
+   */
+  InstantCommand(std::function<void()> toRun,
+                 std::initializer_list<Subsystem*> requirements);
+
+  InstantCommand(InstantCommand&& other) = default;
+
+  InstantCommand(const InstantCommand& other) = default;
+
+  /**
+   * Creates a new InstantCommand with a Runnable that does nothing.  Useful
+   * only as a no-arg constructor to call implicitly from subclass constructors.
+   */
+  InstantCommand();
+
+  void Initialize() override;
+
+  bool IsFinished() final;
+
+ private:
+  std::function<void()> m_toRun;
+};
+}  // namespace frc2