Massive cleanup

- Removed GuildConfigs repository, moved to extensions
- Moved StreamSettings extension to GuildConfig extensions
- namespace NadekoBot.Core has been simplified to NadekoBot in many places (more to come)
- Replaced some raw delete queries with simple linqtodb queries

src/NadekoBot/_Extensions/IUserExtensions.cs

@@ -3,6 +3,7 @@ using NadekoBot.Core.Services.Database.Models;
 using System;
 using System.IO;
 using System.Threading.Tasks;
+using NadekoBot.Services.Database.Models;
 
 namespace NadekoBot.Extensions
 {