Added XboxController class (#140)

Joystick and Gamepad functionality was separated into cleaner interfaces.

wpilibc/shared/include/JoystickBase.h

@@ -0,0 +1,30 @@
+/*----------------------------------------------------------------------------*/
+/* Copyright (c) FIRST 2016. 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 "GenericHID.h"
+
+namespace frc {
+
+/**
+ * Joystick Interface.
+ */
+class JoystickBase : public GenericHID {
+ public:
+  explicit JoystickBase(int port);
+  virtual ~JoystickBase() = default;
+
+  virtual float GetZ(JoystickHand hand = kRightHand) const = 0;
+  virtual float GetTwist() const = 0;
+  virtual float GetThrottle() const = 0;
+
+  virtual bool GetTrigger(JoystickHand hand = kRightHand) const = 0;
+  virtual bool GetTop(JoystickHand hand = kRightHand) const = 0;
+};
+
+}  // namespace frc