[wxGlade] importing custom widgets

[Horst H. <sub...@gn...>]

I'd like to see a section where we can state what is needed to import our 
custom widgets

Problem: if I use custom widgets, I need to import the corresponding module.
Since I chose to "always overwrite" generated modules for several good 
reasons, I would need to manually add the import statement every time I 
change the UI in wxGlade.

Cheers,
Horst