Improve replay metadata and the replay browser

List of changes:

* Better and more filters with new layout, for both mods.

* Rename/Delete/Detele all functionality.

* Simplified ReplayMetadata class considerably by introducing a new
GameInformation data object. The new GameInformation class contains
more information than previously available so the new solution is not
compatible with old replays, meaning it can't read old replays.

* Better and cleaner game information gathering in order to be written
at the end of the replay file.

* Revert changes to ReplayConnection, no longer necessary.

* Better exception message on missing sprites and fonts.

* New "SpawnOccupant" class that holds all the information needed by the
MapPreviewWidget to visualize a spawn point. It was using Session.Client
before and it was necessary to separate it to be able to show information
not available at lobby time.

* Fix keyboard focus UI bug when closing a window would not remove focus.

OpenRA.Game/Widgets/Widget.cs

@@ -258,7 +258,7 @@ namespace OpenRA.Widgets
 			return true;
 		}
 
-		// Remove focus from this widget; return false if you don't want to give it up
+		// Remove focus from this widget; return false to hint that you don't want to give it up
 		public virtual bool YieldMouseFocus(MouseInput mi)
 		{
 			if (Ui.MouseFocusWidget == this)
@@ -267,6 +267,12 @@ namespace OpenRA.Widgets
 			return true;
 		}
 
+		void ForceYieldMouseFocus()
+		{
+			if (Ui.MouseFocusWidget == this && !YieldMouseFocus(default(MouseInput)))
+				Ui.MouseFocusWidget = null;
+		}
+
 		public virtual bool TakeKeyboardFocus()
 		{
 			if (HasKeyboardFocus)
@@ -287,6 +293,12 @@ namespace OpenRA.Widgets
 			return true;
 		}
 
+		void ForceYieldKeyboardFocus()
+		{
+			if (Ui.KeyboardFocusWidget == this && !YieldKeyboardFocus())
+				Ui.KeyboardFocusWidget = null;
+		}
+
 		public virtual string GetCursor(int2 pos) { return "default"; }
 		public string GetCursorOuter(int2 pos)
 		{
@@ -410,6 +422,11 @@ namespace OpenRA.Widgets
 
 		public virtual void Removed()
 		{
+			// Using the forced versions because the widgets
+			// have been removed
+			ForceYieldKeyboardFocus();
+			ForceYieldMouseFocus();
+
 			foreach (var c in Children.OfType<Widget>().Reverse())
 				c.Removed();
 		}