Detect mobile and use react-dnd-touch-backend, add draggable markers

[jspaine]

No description provided.

[Hector101]

@jspaine you mind giving a description on this issue, I'd like to work on it.

[jspaine]

Hi, yeah there are 2 places where react-dnd is used, the questionnaire editor and the driver route editor. I think they both have markers to indicate what's draggable but maybe the route editor still doesn't. And you have to use the touch backend to be able to drag things on mobile browsers.

It's low priority though because those bits are probably not very usable on mobile anyway with the styling it has so far.