Add support for Behaviours (RFC)

[osantana]

Behaviour is something that happens when we interact with a Resource through some Action. We can different kind of behaviours in one Resource like:

• Notification Behavior - everytime that we act on this resource a notification will be triggered by the API.
• Proxy Behavior - proxy interaction to another resource (useful for backward compatible interfaces)
• Persist Behavior - all interactions with the resource will be persisted (stored) in a database
• Transactional Behavior - all-or-nothing behaviour like persist+notification behaviour needs to happen in an atomic fashion
• Change Behavior - every change on this resource/field will reflect in another resource/field