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/src/simulation/SimDigitalInput.cpp

@@ -0,0 +1,21 @@
+/*
+ * SimDigitalInput.cpp
+ *
+ *  Created on: May 28, 2014
+ *      Author: alex
+ */
+
+#include "simulation/SimDigitalInput.h"
+#include "simulation/MainNode.h"
+
+SimDigitalInput::SimDigitalInput(std::string topic) {
+  sub = MainNode::Subscribe("~/simulator/" + topic, &SimDigitalInput::callback,
+                            this);
+  std::cout << "Initialized ~/simulator/" + topic << std::endl;
+}
+
+bool SimDigitalInput::Get() { return value; }
+
+void SimDigitalInput::callback(const msgs::ConstBoolPtr& msg) {
+  value = msg->data();
+}