Better Drag & Drop Support for the Variables-/Fields Window

If I drop a field on the workspace, I’d expect the corresponding table to be created automatically (just like you do it for variables already). However, I really need to place a report container and the correct table to be able to drag & drop.

Promoted to planned status. See https://www.combit.net/en/blog/development/august-2015/enhanced-drag-drop/.