[views] Display only on <button> for drop-down menus
I.e. instead of having two (clickable) buttons, one with the action text (e.g. "add") and one with the caret and only the latter with the effect of toggling the menu, we now only produce one button with both the action text and the caret as content. This way, the user won't get confused when clicking on the text as the menu will toggle.