Drag&Drop of multiple py-files to another script is not allowed

[M. Gronle]

Usually a Python file can be opened if it is dragged and dropped to the command line or another script. However, if multiple files are selected, the drag&drop operation is only allowed on the command line but not on another script. This should be improved.

[Robin Hahn]

fixes #87: multiple files can now be opened by droping on script editor

→ <<cset 7682bef7a727>>