Shady nagy/blazor enhance (#429)

* - Using cdnjs not nuget on bootstrap and signalr.
- Bootstrap modal used for add, edit details and delete.

* EditForm inside modal-content

* Top close button action added

* Removed unused using.

* DeleteCookies moved inside AuthService

* ApplicationCore removed from BlazorAdmin dependencies

* SecureHttpClient removed

* Logout from identity manager added

* last thing to do in logout from admin is LogoutIdentityManager.

* JSRuntime used in AuthService without pass to the functions

* Link fixed when logout from MVC

src/BlazorAdmin/Constants.cs

@@ -3,5 +3,10 @@
     public class Constants
     {
         public const string API_URL = "https://localhost:5099/api/";
+
+        public static class Roles
+        {
+            public const string ADMINISTRATORS = "Administrators";
+        }
     }
 }