Cleaned up robot startup and cleanup/shutdown code (#77)

Cleaned up RobotBase, removed singleton list from SensorBase, and removed unused typedefs and NULL_TASK macro from HAL's Task.hpp. Making the robot class instance static fixed non-POD statics used by the instance during destruction from being destroyed first.

wpilibc/athena/src/DriverStation.cpp

@@ -58,8 +58,6 @@ DriverStation::DriverStation() {
   // It will signal when new packet data is available.
   HALSetNewDataSem(&m_packetDataAvailableCond);
 
-  AddToSingletonList();
-
   m_task = Task("DriverStation", &DriverStation::Run, this);
 }
 
@@ -104,8 +102,8 @@ void DriverStation::Run() {
  * @return Pointer to the DS instance
  */
 DriverStation& DriverStation::GetInstance() {
-  static DriverStation* instance = new DriverStation();
-  return *instance;
+  static DriverStation instance;
+  return instance;
 }
 
 /**