Enable logger.

src/smart_grid/ModelState.hpp

@@ -60,7 +60,7 @@ struct PowerUsage
 
 
 class StateLogger;
-class ModelState : Subject<StateLogger, ModelState>
+class ModelState : public Subject<StateLogger, ModelState>
 {
 public:
     ModelState(SmartGridModell &modell);

src/smg_server.cpp

@@ -48,6 +48,8 @@ void run_sim()
 
     SmartGridModell modell{i2c_device};
     ModelState day{modell};
+    auto log = std::make_shared<StateLogger>();
+    day.attach(log);
 
     MainState main_state {MainState::Simulation};
     SimState sim_state {SimState::Entry};