Use singleton in various classes

src/mango.cr

@@ -1,5 +1,5 @@
+require "./config"
 require "./server"
-require "./context"
 require "./mangadex/*"
 require "option_parser"
 
@@ -24,18 +24,7 @@ OptionParser.parse do |parser|
   end
 end
 
-config = Config.load config_path
-logger = Logger.new config.log_level
-storage = Storage.new config.db_path, logger
-library = Library.new config.library_path, config.scan_interval, logger, storage
-queue = MangaDex::Queue.new config.mangadex["download_queue_db_path"].to_s,
-  logger
-api = MangaDex::API.new config.mangadex["api_url"].to_s
-MangaDex::Downloader.new queue, api, config.library_path,
-  config.mangadex["download_wait_seconds"].to_i,
-  config.mangadex["download_retries"].to_i, logger
+Config.load(config_path).set_current
 
-context = Context.new config, logger, library, storage, queue
-
-server = Server.new context
+server = Server.new
 server.start