Compact Overlay: auto aspect ratio, remember size, auto switch (Issue #278)

Implemented these features (Issue #278):

• Open the compact overlay window with the correct aspect ratio
• Save the size of the compact overlay window, so I don’t have to resize it every time I switch
• Auto toggle to compact overlay when the app window loses focus, so I can switch to another app while I still watching a video very fast

Also, fixed issue #255

app/VLC.Core/ViewModels/Settings/SettingsViewModel.cs

@@ -55,6 +55,9 @@ namespace VLC.ViewModels.Settings
         private bool _autoSwitchToCompactOverlayPiP;
         private int _savedCompactOverlayPiPWidth;
 
+        private const int DEFAULT_COMPACT_OVERLAY_WIDTH = 400;
+        private const bool DEFAULT_AUTO_SWITCH_TO_PIP = false;
+
         public ApplicationTheme ApplicationTheme
         {
             get
@@ -232,7 +235,7 @@ namespace VLC.ViewModels.Settings
             get
             {
                 var autoSwitchToCompactOverlayPiP = ApplicationSettingsHelper.ReadSettingsValue(nameof(AutoSwitchToCompactOverlayPiP));
-                _autoSwitchToCompactOverlayPiP = (bool)(autoSwitchToCompactOverlayPiP ?? false);
+                _autoSwitchToCompactOverlayPiP = (bool)(autoSwitchToCompactOverlayPiP ?? DEFAULT_AUTO_SWITCH_TO_PIP);
 
                 return _autoSwitchToCompactOverlayPiP;
             }
@@ -248,7 +251,7 @@ namespace VLC.ViewModels.Settings
             get
             {
                 var savedWidth = ApplicationSettingsHelper.ReadSettingsValue(nameof(SavedCompactOverlayPiPWidth));
-                _savedCompactOverlayPiPWidth = (int)(savedWidth ?? 400);
+                _savedCompactOverlayPiPWidth = (int)(savedWidth ?? DEFAULT_COMPACT_OVERLAY_WIDTH);
 
                 return _savedCompactOverlayPiPWidth;
             }