Make some classes in internal folder as really to be internal

Author: nvborisenko

dotnet/src/webdriver/Internal/Base64UrlEncoder.cs

@@ -23,7 +23,7 @@ namespace OpenQA.Selenium.Internal
     /// <summary>
     /// Encodes and Decodes strings as Base64Url encoding.
     /// </summary>
-    public static class Base64UrlEncoder
+    internal static class Base64UrlEncoder
     {
         private const char base64PadCharacter = '=';
         private const string doubleBase64PadCharacter = "==";

dotnet/src/webdriver/Internal/IWebDriverObjectReference.cs

@@ -16,10 +16,7 @@
 // limitations under the License.
 // </copyright>
 
-using System;
 using System.Collections.Generic;
-using System.Linq;
-using System.Text;
 
 namespace OpenQA.Selenium.Internal
 {

dotnet/src/webdriver/Internal/PortUtilities.cs

@@ -24,7 +24,7 @@ namespace OpenQA.Selenium.Internal
     /// <summary>
     /// Encapsulates methods for working with ports.
     /// </summary>
-    public static class PortUtilities
+    internal static class PortUtilities
     {
         /// <summary>
         /// Finds a random, free port to be listened on.

dotnet/src/webdriver/Internal/ResourceUtilities.cs

@@ -16,9 +16,6 @@
 // limitations under the License.
 // </copyright>
 
-using System;
-using System.Collections.Generic;
-using System.Diagnostics;
 using System.Globalization;
 using System.IO;
 using System.Reflection;

dotnet/src/webdriver/Internal/ReturnedCookie.cs

@@ -24,7 +24,7 @@ namespace OpenQA.Selenium.Internal
     /// <summary>
     /// Represents a cookie returned to the driver by the browser.
     /// </summary>
-    public class ReturnedCookie : Cookie
+    internal class ReturnedCookie : Cookie
     {
 
         /// <summary>