Rename Root to Model, and any other class named Model to a more specific class name

Specifically, the refactoring entails:

• de.tudresden.inf.st.eraser.jastadd.model.Root → de.tudresden.inf.st.eraser.jastadd.model.Model
• de.tudresden.inf.st.eraser.feedbackloop.api.model.Model → de.tudresden.inf.st.eraser.feedbackloop.api.model.EncogModel