Startup, workers and configuration overhaul!

[YuukanOO]

This one is way to big and I should have split it.

There's a lot of refactoring going there:

• The application layer is now exposed with a bus used by http handlers
• The internal/worker does not exist anymore and has been replaced with the bus.Scheduler
• The bus also handle domain events dispatching
• The configuration is now only saved if it doesn't exist yet
• The logger can now be configured with the new log section
• The async package has been refactored to make things simpler again (or at least I hope so)