Use a predetermined default password length field

GUI/GeneratePassword.Designer.cs

@@ -67,7 +67,7 @@ partial class GeneratePassword
         // 
         passwordLength.Location = new Point(12, 77);
         passwordLength.Name = "passwordLength";
-        passwordLength.PlaceholderText = "16";
+        passwordLength.PlaceholderText = PasswordGenerator.DEFAULT_LENGTH;
         passwordLength.Size = new Size(156, 23);
         passwordLength.TabIndex = 3;
         // 
@@ -132,4 +132,4 @@ partial class GeneratePassword
     private CheckBox noSymbols;
     private Button generate;
     private Button cancel;
-}
+}