refactors and more UI

UI/Dialogs/DataOpen.axaml

@@ -0,0 +1,19 @@
+<UserControl xmlns="https://github.com/avaloniaui"
+        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
+        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
+        xmlns:local="clr-namespace:MercuryConverter.UI.Dialogs"
+        xmlns:progRing="clr-namespace:AvaloniaProgressRing;assembly=AvaloniaProgressRing"
+        x:Class="MercuryConverter.UI.Dialogs.DataOpen"
+>
+    <StackPanel Margin="12">
+        <TextBlock Text="Select your data folder..."/>
+        <progRing:ProgressRing Foreground="{DynamicResource SystemBaseMediumColor}"
+            Width="36" 
+            Height="36"
+            IsActive="True"
+            HorizontalAlignment="Center"
+            Margin="0,15,0,0"/>
+    </StackPanel>
+
+</UserControl>