Sc 160/private calls and bugs cleanup

Cleaned up controller w.r.t. PEP-8, private attribute access and some small bugs. Also adapted other classes accordingly.

umbra/statistics.py

@@ -25,6 +25,10 @@ class Statistics:
         self._strategy = AnchorAlgorithm(self._mistake_finder)
         self._last_used_strategy = None
 
+    @property
+    def mistake_counter(self):
+        return self._mistake_counter
+
     @property
     def last_used_strategy(self):
         """Getter for the last used strategy, which is the strategy ran