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/Services/DbService.cs

@@ -4,6 +4,7 @@ using NadekoBot.Core.Services.Database;
 using System;
 using System.IO;
 using System.Linq;
+using NadekoBot.Services.Database;
 
 namespace NadekoBot.Core.Services
 {