Introduce inheritable Profiles and Managers

- There's always a single Profile choosen
- There are many Managers changing settings
  depending on environment
- Improve and re-use mappings between profiles
- Introduce Steam Profile to be used when
  in Steam Big Picture or Steam Game

SteamController/Managers/ProcessManager.cs

@@ -0,0 +1,47 @@
+using System.Diagnostics;
+
+namespace SteamController.Managers
+{
+    public sealed class ProcessManager : Manager
+    {
+        public static readonly String[] ActivationProcessNames = new String[]
+        {
+            "Playnite.FullscreenApp"
+        };
+
+        private bool activated;
+
+        private Process? FindActivationProcess()
+        {
+            foreach (var processName in ActivationProcessNames)
+            {
+                var process = Process.GetProcessesByName(processName).FirstOrDefault();
+                if (process is not null)
+                    return process;
+            }
+
+            return null;
+        }
+
+        public override void Tick(Context context)
+        {
+            // React to state change
+            if (FindActivationProcess() is not null)
+            {
+                if (!activated)
+                {
+                    activated = true;
+                    context.RequestDesktopMode = false;
+                }
+            }
+            else
+            {
+                if (activated)
+                {
+                    activated = false;
+                    context.RequestDesktopMode = true;
+                }
+            }
+        }
+    }
+}