[oozie] Many-pronged forks are difficult to read in Editor

When a workflow forks in many ways (quite common!) the Editor shows the entries stacked in rows (see attached). This clashes with the implied behavior that dependencies in the Editor run top to bottom.

One suggestion might be to add horizontal scrolling to the section so that wide workflows could be visible without being squashed too thin or without breaking the vertical dependency notion. Another suggestion might be to use a more flexible icon-and-arrow interface, much like the well known ETL workflow tools such as Informatica and DataStage.