Differentiate form data from persisted data

[wsargent]

This example is using the computer ebean DB model as the form data. This is not great, because it means that persistence methods are exposed to the front end template and there's inappropriate coupling between database fields and form fields.

https://github.com/playframework/play-java-ebean-example/blob/2.6.x/app/controllers/HomeController.java#L94