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/Modules/Music/Common/Impl/MultimediaTimer.cs

@@ -2,7 +2,7 @@
 using System.Runtime.InteropServices;
 using Serilog;
 
-namespace NadekoBot.Core.Modules.Music.Common
+namespace NadekoBot.Modules.Music.Common
 {
     public sealed class MultimediaTimer : IDisposable
     {