Add SteamController implementation

This adds a Steam Shortcuts, Desktop Mode, and X360 Emulation
- Supports all Steam Shortcuts (including on-screen keyboard, and brightness)
- Supports Desktop mode (with a scroll on left pad and left stick), and trackpoint (on right stick)
- Supports X360 mode: hold Options for 1s to switch between Desktop and X360
- Holding Steam button enables Desktop like controls and stops passing all inputs to X360

ExternalHelpers/WindowsSettingsBrightnessController.cs

@@ -12,6 +12,14 @@ namespace PowerControl.Helpers
     /// </summary>
     public static class WindowsSettingsBrightnessController
     {
+        public static void Increase(int brightness)
+        {
+            var current = Get();
+            current += brightness;
+            current = Math.Clamp(current, 0, 100);
+            Set(current);
+        }
+
         public static int Get(double roundValue = 10.0)
         {
             return (int)(Math.Round(Get() / roundValue) * roundValue);