Databindings - Added conditional databindings

Conditions - Added easy method for null-handling in operators

src/Artemis.UI.Shared/DataModelVisualization/Input/DataModelDynamicView.xaml

@@ -36,8 +36,7 @@
                 ToolTip="{Binding SelectedPropertyViewModel.DisplayPropertyPath}"
                 IsEnabled="{Binding IsEnabled}"
                 HorizontalAlignment="Left"
-                Click="PropertyButton_OnClick"
-                Visibility="{Binding ShowFreeInput, Converter={x:Static s:BoolToVisibilityConverter.InverseInstance}, Mode=OneWay}">
+                Click="PropertyButton_OnClick">
             <Button.ContextMenu>
                 <ContextMenu ItemsSource="{Binding DataModelViewModel.Children}" IsOpen="{Binding IsDataModelViewModelOpen, Mode=OneWayToSource}">
                     <ContextMenu.ItemContainerStyle>

src/Artemis.UI.Shared/DataModelVisualization/Input/DataModelStaticView.xaml

@@ -32,12 +32,12 @@
             <Grid>
                 <StackPanel Visibility="{Binding Value, Converter={StaticResource NullToVisibilityConverter}}" Orientation="Horizontal">
                     <TextBlock FontWeight="Light"
-                               Text="{Binding TargetPropertyViewModel.PropertyDescription.Prefix}"
-                               Visibility="{Binding TargetPropertyViewModel.PropertyDescription.Prefix, Converter={StaticResource NullToVisibilityConverter}}" />
+                               Text="{Binding TargetDescription.Prefix}"
+                               Visibility="{Binding TargetDescription.Prefix, Converter={StaticResource NullToVisibilityConverter}}" />
                     <ContentControl s:View.Model="{Binding DisplayViewModel}" VerticalAlignment="Stretch" HorizontalAlignment="Stretch" />
                     <TextBlock FontWeight="Light" 
-                               Text="{Binding TargetPropertyViewModel.PropertyDescription.Affix}"
-                               Visibility="{Binding TargetPropertyViewModel.PropertyDescription.Affix, Converter={StaticResource NullToVisibilityConverter}}" />
+                               Text="{Binding TargetDescription.Affix}"
+                               Visibility="{Binding TargetDescription.Affix, Converter={StaticResource NullToVisibilityConverter}}" />
                 </StackPanel>
 
                 <TextBlock FontStyle="Italic" Visibility="{Binding Value, Converter={StaticResource NullToVisibilityConverter}, ConverterParameter=Inverted}">