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/DigitalInput.h

@@ -0,0 +1,44 @@
+/*----------------------------------------------------------------------------*/
+/* 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 "LiveWindow/LiveWindowSendable.h"
+#include "simulation/SimDigitalInput.h"
+
+#include <memory>
+
+/**
+ * Class to read a digital input.
+ *
+ * This class will read digital inputs and return the current value on the
+ * channel. Other devices such as encoders, gear tooth sensors, etc. that are
+ * implemented elsewhere will automatically allocate digital inputs and outputs
+ * as required. This class is only for devices like switches etc. that aren't
+ * implemented anywhere else.
+ */
+class DigitalInput : public LiveWindowSendable {
+ public:
+  explicit DigitalInput(uint32_t channel);
+  virtual ~DigitalInput() = default;
+  uint32_t Get() const;
+  uint32_t GetChannel() const;
+
+  void UpdateTable() override;
+  void StartLiveWindowMode() override;
+  void StopLiveWindowMode() override;
+  std::string GetSmartDashboardType() const override;
+  void InitTable(std::shared_ptr<ITable> subTable) override;
+  std::shared_ptr<ITable> GetTable() const override;
+
+ private:
+  uint32_t m_channel;
+  bool m_lastValue;
+  SimDigitalInput* m_impl;
+
+  std::shared_ptr<ITable> m_table;
+};