- 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/MutedUserId.cs

@@ -0,0 +1,19 @@
+namespace NadekoBot.Core.Services.Database.Models
+{
+    public class MutedUserId : DbEntity
+    {
+        public ulong UserId { get; set; }
+
+        public override int GetHashCode()
+        {
+            return UserId.GetHashCode();
+        }
+
+        public override bool Equals(object obj)
+        {
+            return obj is MutedUserId mui
+                ? mui.UserId == UserId
+                : false;
+        }
+    }
+}