[oozie] Improve UX of entering args to distcp action in workflow editor

When adding a distcp action to a workflow in the editor, we are prompted for source and destination arguments first. Then to add additional arguments, we click the "+" button and extra text boxes appear with placeholder text "Options first, then source / destination paths".

Because the order is important, the new text boxes should either appear before the existing ones, keeping the paths at the end. Otherwise it is necessary to cut and paste to reorder what was already entered. Alternatively the source/destination entries could be kept separate from the additional arguments.