Dev/overlay control (#278)

* Creating a control for the overlay

* using Interactivity

* trying to bind by reference

* fix bindings

* remove unused packages

* Move getter/setter to show method

* Convert to AutoProperty

* Make text copied notification configurable

* cache settings, removed unused file

FluentTerminal.App.ViewModels/OverlayViewModel.cs

@@ -0,0 +1,51 @@
+using FluentTerminal.App.Services;
+using GalaSoft.MvvmLight;
+using System;
+
+namespace FluentTerminal.App.ViewModels
+{
+    public class OverlayViewModel : ViewModelBase
+    {
+        private readonly IDispatcherTimer _overlayTimer;
+        private bool _showOverlay;
+        private string _overlayContent;
+
+        public OverlayViewModel(IDispatcherTimer dispatcherTimer)
+        {
+            _overlayTimer = dispatcherTimer;
+            _overlayTimer.Interval = new TimeSpan(0, 0, 2);
+            _overlayTimer.Tick += OnResizeOverlayTimerFinished;
+        }
+
+        public bool ShowOverlay
+        {
+            get => _showOverlay;
+            set => Set(ref _showOverlay, value);
+        }
+
+        public string OverlayContent
+        {
+            get => _overlayContent;
+            set => Set(ref _overlayContent, value);
+        }
+
+        public void Show(string message)
+        {
+            OverlayContent = message; 
+            ShowOverlay = true;
+
+            if (_overlayTimer.IsEnabled)
+            {
+                _overlayTimer.Stop();
+            }
+            _overlayTimer.Start();
+        }
+
+        private void OnResizeOverlayTimerFinished(object sender, object e)
+        {
+            _overlayTimer.Stop();
+            ShowOverlay = false;
+        }
+
+    }
+}