Added some tests

Removed false first group, replaced it a button in the header
Code refactor

ModernKeePassApp.Test/Mock/LicenseServiceMock.cs

@@ -0,0 +1,31 @@
+using System;
+using System.Collections.Generic;
+using System.Threading.Tasks;
+using Windows.ApplicationModel;
+using Windows.ApplicationModel.Store;
+using ModernKeePass.Interfaces;
+
+namespace ModernKeePassApp.Test.Mock
+{
+    public class LicenseServiceMock: ILicenseService
+    {
+        public IReadOnlyDictionary<string, ProductListing> Products { get; }
+
+        public LicenseServiceMock()
+        {
+            try
+            {
+                var proxyFile = Package.Current.InstalledLocation.GetFileAsync("data\\WindowsStoreProxy.xml").GetAwaiter().GetResult();
+                CurrentAppSimulator.ReloadSimulatorAsync(proxyFile).GetAwaiter().GetResult();
+            }
+            catch { }
+            var listing = CurrentAppSimulator.LoadListingInformationAsync().GetAwaiter().GetResult();
+            Products = listing.ProductListings;
+        }
+
+        public Task<int> Purchase(string addOn)
+        {
+            throw new System.NotImplementedException();
+        }
+    }
+}