Refactor the event and actions workflow

Clean up the names and concerns of the project.
Hook reception and dispatched is now based around a few core concepts:
* A Payload class is parsing the data received from a Webhook endpoint and extracts data from it
* Extracted payload data is composed of Event objects identified by their type
* Each event can result in one or multiple operations defined in Action classes
Cleanup initializers naming
Add a Project model, persisted in database

Hook URLs are now differentiated by project.
The new URL format is: /hooks/:project_id/:service_name
Make the actions list more dynamic

This change will permit the implementation of dynamic triggers.