Replace "Save" button by more honest "Next" button in training view

[acidAnn]

At the moment, the form in the training view has the same structure as the actual annotation view and therefore contains a "Save" button ("Speichern"). However, in this view, the submitted data is not saved as the view is solely considered as a playing ground.
A "Next" button ("Weiter") instead of "Save" would reflect this much better.