Re-organize style sheets and add StyleSpace.

Content.Client/UserInterface/Stylesheets/IStylesheetManager.cs

@@ -0,0 +1,12 @@
+using Robust.Client.UserInterface;
+
+namespace Content.Client.UserInterface.Stylesheets
+{
+    public interface IStylesheetManager
+    {
+        Stylesheet SheetNano { get; }
+        Stylesheet SheetSpace { get; }
+
+        void Initialize();
+    }
+}