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/simulation/SimDigitalInput.h

@@ -0,0 +1,31 @@
+/*----------------------------------------------------------------------------*/
+/* Copyright (c) FIRST 2014-2016. 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.                                                               */
+/*----------------------------------------------------------------------------*/
+
+#ifndef _SIM_DIGITAL_INPUT_H
+#define _SIM_DIGITAL_INPUT_H
+
+#include <gazebo/transport/transport.hh>
+#include "simulation/gz_msgs/msgs.h"
+
+using namespace gazebo;
+
+class SimDigitalInput {
+ public:
+  SimDigitalInput(std::string topic);
+
+  /**
+   * @return The value of the potentiometer.
+   */
+  bool Get();
+
+ private:
+  bool value;
+  transport::SubscriberPtr sub;
+  void callback(const msgs::ConstBoolPtr& msg);
+};
+
+#endif