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/button/JoystickButton.h

@@ -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.                                                               */
+/*----------------------------------------------------------------------------*/
+
+#pragma once
+#include <frc/GenericHID.h>
+
+#include "Button.h"
+
+namespace frc2 {
+/**
+ * A class used to bind command scheduling to joystick button presses.  Can be
+ * composed with other buttons with the operators in Trigger.
+ *
+ * @see Trigger
+ */
+class JoystickButton : public Button {
+ public:
+  /**
+   * Creates a JoystickButton that commands can be bound to.
+   *
+   * @param joystick The joystick on which the button is located.
+   * @param buttonNumber The number of the button on the joystic.
+   */
+  explicit JoystickButton(frc::GenericHID* joystick, int buttonNumber)
+      : m_joystick{joystick}, m_buttonNumber{buttonNumber} {}
+
+  bool Get() const override { return m_joystick->GetRawButton(m_buttonNumber); }
+
+ private:
+  frc::GenericHID* m_joystick;
+  int m_buttonNumber;
+};
+}  // namespace frc2