Profile editor - Clarified which LEDs are part of the selected layer

Profile editor - Re-implemented LED dimming
Profile editor - Hide layer bounds of unselected layers
Profile editor - Dim layer shapes of unselected layers (option to hide them NYI)
Profile editor - Disable edit tool when no layer is selected or the selected layer has no LEDs
Gradient picker - Fixed the preview being at a slight angle
Color brush - Fixed the gradient being at a 45 degree angle
Settings - Added color scheme option to manually switch between light and dark

src/Artemis.UI.Shared/Screens/GradientEditor/GradientEditorView.xaml

@@ -53,7 +53,9 @@
                            utilities:SizeObserver.ObservedWidth="{Binding PreviewWidth, Mode=OneWayToSource}">
                     <Rectangle.Fill>
                         <LinearGradientBrush
-                            GradientStops="{Binding ColorGradient.Stops, Converter={StaticResource ColorGradientToGradientStopsConverter}}" />
+                            GradientStops="{Binding ColorGradient.Stops, Converter={StaticResource ColorGradientToGradientStopsConverter}}" 
+                            EndPoint="1,0"
+                            StartPoint="0,0"/>
                     </Rectangle.Fill>
                 </Rectangle>