filter deleted pages and modules in the router, provide support for cascading aspect of style sheets, replace ResourceDeclaration concept with ResourceLevel

Oqtane.Shared/Enums/ResourceDeclaration.cs

@@ -1,5 +1,8 @@
+using System;
+
 namespace Oqtane.Shared
 {
+    [Obsolete("ResourceDeclaration is deprecated", false)]
     public enum ResourceDeclaration
     {
         Local,

Oqtane.Shared/Enums/ResourceLevel.cs

@@ -0,0 +1,8 @@
+namespace Oqtane.Shared
+{
+    public enum ResourceLevel
+    {
+        Page,
+        Module
+    }
+}