- 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/Extensions/DbExtensions.cs

@@ -0,0 +1,12 @@
+using System.Linq;
+using Microsoft.EntityFrameworkCore;
+using NadekoBot.Core.Services.Database.Models;
+
+namespace NadekoBot.Db
+{
+    public static class DbExtensions
+    {
+        public static T GetById<T>(this DbSet<T> set, int id) where T: DbEntity
+            => set.FirstOrDefault(x => x.Id == id);
+    }
+}