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/athena/include/Notifier.h

@@ -0,0 +1,56 @@
+/*----------------------------------------------------------------------------*/
+/* 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 <functional>
+
+#include "ErrorBase.h"
+#include "HAL/cpp/priority_mutex.h"
+
+typedef std::function<void()> TimerEventHandler;
+
+class Notifier : public ErrorBase {
+ public:
+  explicit Notifier(TimerEventHandler handler);
+
+  template <typename Callable, typename Arg, typename... Args>
+  Notifier(Callable&& f, Arg&& arg, Args&&... args)
+      : Notifier(std::bind(std::forward<Callable>(f), std::forward<Arg>(arg),
+                           std::forward<Args>(args)...)) {}
+
+  virtual ~Notifier();
+
+  Notifier(const Notifier&) = delete;
+  Notifier& operator=(const Notifier&) = delete;
+
+  void StartSingle(double delay);
+  void StartPeriodic(double period);
+  void Stop();
+
+ private:
+  // update the HAL alarm
+  void UpdateAlarm();
+  // HAL callback
+  static void Notify(uint64_t currentTimeInt, void* param);
+
+  // held while updating process information
+  priority_mutex m_processMutex;
+  // HAL handle
+  void* m_notifier;
+  // address of the handler
+  TimerEventHandler m_handler;
+  // the absolute expiration time
+  double m_expirationTime = 0;
+  // the relative time (either periodic or single)
+  double m_period = 0;
+  // true if this is a periodic event
+  bool m_periodic = false;
+
+  // held by interrupt manager task while handler call is in progress
+  priority_mutex m_handlerMutex;
+};