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/Administration/Services/GuildTimezoneService.cs

@@ -67,7 +67,7 @@ namespace NadekoBot.Modules.Administration.Services
         {
             using (var uow = _db.GetDbContext())
             {
-                var gc = uow.GuildConfigs.ForId(guildId, set => set);
+                var gc = uow._context.GuildConfigsForId(guildId, set => set);
 
                 gc.TimeZoneId = tz?.Id;
                 uow.SaveChanges();