Major OpenDatabaseUserControl refactor, now has proper ViewModel

Status text and password box border colors are updated according to database status
Update composite key in Settings work
Some code cleanup

ModernKeePass/Pages/SettingsPageFrames/SettingsSecurityPage.xaml

@@ -0,0 +1,14 @@
+<Page
+    x:Class="ModernKeePass.Pages.SettingsSecurityPage"
+    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
+    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+    xmlns:local="using:ModernKeePass.Controls"
+    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
+    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
+    mc:Ignorable="d">
+
+    <StackPanel Background="{ThemeResource ApplicationPageBackgroundThemeBrush}">
+        <TextBlock Text="Change database security options" />
+        <local:OpenDatabaseUserControl UpdateKey="True" />
+    </StackPanel>
+</Page>

ModernKeePass/Pages/SettingsPageFrames/SettingsSecurityPage.xaml.cs

@@ -0,0 +1,15 @@
+// The Blank Page item template is documented at http://go.microsoft.com/fwlink/?LinkId=234238
+
+namespace ModernKeePass.Pages
+{
+    /// <summary>
+    /// An empty page that can be used on its own or navigated to within a Frame.
+    /// </summary>
+    public sealed partial class SettingsSecurityPage
+    {
+        public SettingsSecurityPage()
+        {
+            InitializeComponent();
+        }
+    }
+}