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/POVButton.h

@@ -0,0 +1,41 @@
+/*----------------------------------------------------------------------------*/
+/* 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 POV presses.  Can be
+ * composed with other buttons with the operators in Trigger.
+ *
+ * @see Trigger
+ */
+class POVButton : public Button {
+ public:
+  /**
+   * Creates a POVButton that commands can be bound to.
+   *
+   * @param joystick The joystick on which the button is located.
+   * @param angle The angle of the POV corresponding to a button press.
+   * @param povNumber The number of the POV on the joystick.
+   */
+  POVButton(frc::GenericHID* joystick, int angle, int povNumber = 0)
+      : m_joystick{joystick}, m_angle{angle}, m_povNumber{povNumber} {}
+
+  bool Get() const override {
+    return m_joystick->GetPOV(m_povNumber) == m_angle;
+  }
+
+ private:
+  frc::GenericHID* m_joystick;
+  int m_angle;
+  int m_povNumber;
+};
+}  // namespace frc2