Renamed folders for consistency, using sim/athena/shared schema (#27)

Rename the following folders:
hal/lib/Athena -> hal/lib/athena
hal/lib/Desktop -> hal/lib/sim
hal/lib/Shared -> hal/lib/shared
wpilibc/Athena -> wpilibc/athena
wpilibc/simulation -> wpilibc/sim

Windows users may need to run gradlew clean after updating.

wpilibc/sim/include/SafePWM.h

@@ -0,0 +1,40 @@
+/*----------------------------------------------------------------------------*/
+/* Copyright (c) FIRST 2008-2016. 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 <memory>
+#include "MotorSafety.h"
+#include "MotorSafetyHelper.h"
+#include "PWM.h"
+
+/**
+ * A safe version of the PWM class.
+ *
+ * It is safe because it implements the MotorSafety interface that provides
+ * timeouts in the event that the motor value is not updated before the
+ * expiration time. This delegates the actual work to a MotorSafetyHelper
+ * object that is used for all objects that implement MotorSafety.
+ */
+class SafePWM : public PWM, public MotorSafety {
+ public:
+  explicit SafePWM(uint32_t channel);
+  virtual ~SafePWM() = default;
+
+  void SetExpiration(float timeout);
+  float GetExpiration() const;
+  bool IsAlive() const;
+  void StopMotor();
+  bool IsSafetyEnabled() const;
+  void SetSafetyEnabled(bool enabled);
+  void GetDescription(std::ostringstream& desc) const;
+
+  virtual void SetSpeed(float speed);
+
+ private:
+  std::unique_ptr<MotorSafetyHelper> m_safetyHelper;
+};