Remove unused using statements and fix typos

Author: nemanjarogic

src/AdditionalPatterns/NullObject/NullObjectLibrary/SmartphoneApplicationExample/SmartphoneApplicationExecutor.cs

@@ -18,8 +18,8 @@ public static void Execute()
             gmail.Open();
             gmail.Close();
 
-            // Null exception will not be thrown if application is not found
-            // by specified process ID. We return default (NULL) object.
+            // Null exception won't be thrown if an application with the specified process ID can't be found.
+            // In that case, default (NULL) object will be returned.
             var youtube = applicationRepository.Find(invalidProcessId);
             youtube.Open();
             youtube.Close();

src/BehavioralPatterns/ChainOfResponsibility/ChainOfResponsibilityLibrary/LoggingExample/Common/Logger.cs

@@ -1,6 +1,4 @@
-using System;
-
-namespace ChainOfResponsibilityLibrary.LoggingExample.Common
+namespace ChainOfResponsibilityLibrary.LoggingExample.Common
 {
     public abstract class Logger
     {

src/BehavioralPatterns/ChainOfResponsibility/ChainOfResponsibilityLibrary/LoggingExample/LoggingExecutor.cs

@@ -13,9 +13,9 @@ public static void Execute()
 
             Logger loggerChain = InitializeLoggerChain();
 
-            var infoMessage = "This is an information.";
-            var debugMessage = "This is an debug level information.";
-            var errorMessage = "This is an error information.";
+            var infoMessage = "This is information.";
+            var debugMessage = "This is debug level information.";
+            var errorMessage = "This is error information.";
 
             loggerChain.Log(LogLevel.Info, infoMessage);
             Console.WriteLine();

src/BehavioralPatterns/Strategy/StrategyLibrary/SortingExample/Strategies/SortByLastName.cs

@@ -1,5 +1,4 @@
-using System;
-using System.Collections.Generic;
+using System.Collections.Generic;
 using StrategyLibrary.SortingExample.Strategies.Common;
 
 namespace StrategyLibrary.SortingExample.Strategies