Refactored #addStage and #addServer to explicitly take an instance instead of automagically creating one. Less singleton-pattern, more flexibility.
Refactored out Config#config to the Base class and extended Config with Base. Stage has thus also a #config method now
Refactored Config#addStage to use Base#_addInstanceToCollection
Server inherits Base and thus also supports server-specific events and #config
Moved optional `new` logic to Base class