Form actions
The row every form ends with, in five shapes: the one core puts at the foot of an entity form, one of everything that can turn up in such a row -- which is also the test of what happens when it wraps -- the dropbutton buttons are folded into when they are given a `#dropbutton`, the actions of a confirmation form, where the primary button is the destructive one, and an actions element on a line with the field it filters. Nothing is saved: each button that submits says which one was pressed.