Suggest to save ViewDefinition when leaving Form

[spicyfalafel]

1. Get existing VD -> saved-vd := current-vd
2. New vd or import -> nothing
3. Save button -> saved-vd := current-vd
4. Click on navigation or breadcrumb -> check if current-vd == saved-vd. if true, exit. If not, do not exit. Show modal with "no save"

on-finish event is useless in this case.