Implement a Crud.startup event

It maps directly to Component::startup()

Renamed Crud.init to Crud.initialize to be more aligned with the terms used
in Components

The flow of events is now:

* __constructor (called in CrudComponent::_loadListener)
* startup (called in CrudComponent::initialize)
* initialize (called in CrudComponent::initAction)
* - the normal flow as we know it -

Obviously due to the flow of events, it's possible that properties changes between startup() and initialize()
and thus the `_container` property will be replaced in `Crud.initialize` so `_model` and other properties that
may have changed between startup() and initialize() is reflected internally
Merge pull request #45 from jippi/feature/listener-startup-event

Implement a Crud.startup event