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/PIDCommand.h

@@ -0,0 +1,79 @@
+/*----------------------------------------------------------------------------*/
+/* 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 "frc/controller/PIDController.h"
+#include "frc2/command/CommandBase.h"
+#include "frc2/command/CommandHelper.h"
+
+namespace frc2 {
+/**
+ * A command that controls an output with a PIDController.  Runs forever by
+ * default - to add exit conditions and/or other behavior, subclass this class.
+ * The controller calculation and output are performed synchronously in the
+ * command's execute() method.
+ *
+ * @see PIDController
+ */
+class PIDCommand : public CommandHelper<CommandBase, PIDCommand> {
+ public:
+  /**
+   * Creates a new PIDCommand, which controls the given output with a
+   * PIDController.
+   *
+   * @param controller        the controller that controls the output.
+   * @param measurementSource the measurement of the process variable
+   * @param setpointSource   the controller's reference (aka setpoint)
+   * @param useOutput         the controller's output
+   * @param requirements      the subsystems required by this command
+   */
+  PIDCommand(PIDController controller,
+             std::function<double()> measurementSource,
+             std::function<double()> setpointSource,
+             std::function<void(double)> useOutput,
+             std::initializer_list<Subsystem*> requirements);
+
+  /**
+   * Creates a new PIDCommand, which controls the given output with a
+   * PIDController with a constant setpoint.
+   *
+   * @param controller        the controller that controls the output.
+   * @param measurementSource the measurement of the process variable
+   * @param setpoint         the controller's setpoint (aka setpoint)
+   * @param useOutput         the controller's output
+   * @param requirements      the subsystems required by this command
+   */
+  PIDCommand(PIDController controller,
+             std::function<double()> measurementSource, double setpoint,
+             std::function<void(double)> useOutput,
+             std::initializer_list<Subsystem*> requirements);
+
+  PIDCommand(PIDCommand&& other) = default;
+
+  PIDCommand(const PIDCommand& other) = default;
+
+  void Initialize() override;
+
+  void Execute() override;
+
+  void End(bool interrupted) override;
+
+  /**
+   * Returns the PIDController used by the command.
+   *
+   * @return The PIDController
+   */
+  PIDController& getController();
+
+ protected:
+  PIDController m_controller;
+  std::function<double()> m_measurement;
+  std::function<double()> m_setpoint;
+  std::function<void(double)> m_useOutput;
+};
+}  // namespace frc2