Integrate wilrich/logregacc into master

contrib/Python/cntk/examples/LogReg/logreg_numpy.py

@@ -69,7 +69,7 @@ def train_eval_logistic_regression_with_numpy(criterion_name=None,
     my_sgd = C.SGDParams(epoch_size=0, minibatch_size=25,
             learning_rates_per_mb=0.1, max_epochs=3)
 
-    with C.LocalExecutionContext('logreg', clean_up=False) as ctx:
+    with C.LocalExecutionContext('logreg', clean_up=True) as ctx:
         ctx.device_id = device_id
 
         ctx.train(