New dagre-d3 designer improvements

First of all great work on this!!!!
Solved two or three issues I had before it :)
Lines not overlap, zoom in and out, etc.... Very nice :).

However, and this is my personal feeling, I'm kind of confused when I see workflow canvas having items and don't see any scrollbars.
Scrollbars kind of give you a hint where you are on the designer canvas and without them I kind of have a "where am I feeling" all the time.

In addition, probably connected, to not having scrollbars....
I like scrolling with mouse drag but would definitely like being able to scroll using mouse scroll wheel (both horizontally and vertically).
I'm so used to it when it comes to scrolling in all other different pages/programs I use that I keep zooming in and out automatically when I want to scroll.....

To summarize, can we have?:
- scrollbars
- mouse wheel do scrolling (vertical and horizontal if supported by mouse) and CTRL + mousewheel do zoom in out (this seems to be "standard" in many programs)

All in all, excellent work, if you can do something with these "minor" problems I have, would be great :)
Thanks.