- Database namespace is now NadekoBot.Db

- Db related code is now in src/NadekoBot/Db
- Finished major part of the db refactor, but many optimizations are left to be made

src/NadekoBot/Db/Models/DbEntity.cs

@@ -0,0 +1,12 @@
+using System;
+using System.ComponentModel.DataAnnotations;
+
+namespace NadekoBot.Core.Services.Database.Models
+{
+    public class DbEntity
+    {
+        [Key]
+        public int Id { get; set; }
+        public DateTime? DateAdded { get; set; } = DateTime.UtcNow;
+    }
+}