Adds some VM tests

New tooltip in Textbox with button control
New welcome page in Settings (shown when noting is selected)
Settings are now grouped

ModernKeePass/Common/DatabaseHelper.cs

@@ -1,6 +1,5 @@
 using System;
 using Windows.Storage;
-using Windows.Storage.AccessCache;
 using Windows.UI.Xaml.Controls;
 using ModernKeePass.Exceptions;
 using ModernKeePass.Interfaces;