[Editor] Drop level files to opened world map as an entrance point

[Wohlstand]

On a quick think about importer fixes / reworks, I have got an idea: When working with a world map, why not to take a level file from a file manager (Explorer on windows, Finder on macOS, or Dolphin/Nautilus/Thunar/etc. on Linux & Co, etc.) and put it into world map and put the entrance point that will use it.

[Alucard648]

And how editor would work after so-called mass-importing levels? Just spawn level entrance points with levels assigned in properties? Imho, the following things should be accounted for.

• [ ] Placement of entrance points with imported levels. I am suggesting to either place a selected group of level points somewhere in the middle of the camera view. Alternative idea is to keep group of levels in the clipboard. All that it needs is the message that explains that imported levels are stored in the clipboard.

• [ ] Tooltip that indicates which level file is assigned to practicular entrance point. This allows quicker placement of imported levels to desired locations and minimize causes of such error as wrong level assigned to entrance point.