Fixed files node model, use passed entity values rather than state values

This appears to be a bug, when uploading a file, ControllerBehaviorAttachable::109 passes the file data via the context.

ModelAbstract->create() passes the file data (array) to an "entity" property on a new context

ModelNodes->_actionCreate receives the context as an argument, currently looks in the state property, rather than the entity property.