Add Drag and drop import to slicelet?

[lassoan (Andras Lasso)]

@Amine

drag and drop function to a slicelet

We do not recommend to implement slicelets without main window for many reasons. Slicer now has built-in scripts to strip down the default main window from Python (see here). For more control, you can create a custom application in C++ (based on a default main window that you can customize any way you need).