Finished adding basic category adding functionality

OpenArchival.Database/ArchiveEntryProvider.cs

@@ -0,0 +1,12 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace OpenArchival.Database
+{
+    internal class ArchiveEntryProvider
+    {
+    }
+}