adopt more of the migrations conventions

Oqtane.Server/Infrastructure/SiteMigration/ExampleSiteMigration.cs

@@ -0,0 +1,18 @@
+using Oqtane.Models;
+
+namespace Oqtane.Infrastructure
+{
+    [SiteMigration("localhost:44357", "01.00.00")]
+    public class ExampleSiteMigration : ISiteMigration
+    {
+        void ISiteMigration.Up(Site site, Alias alias)
+        {
+            // execute some version-specific upgrade logic for the site here such as adding pages, modules, content, etc...
+        }
+
+        void ISiteMigration.Down(Site site, Alias alias)
+        {
+            // not implemented
+        }
+    }
+}