Fix vfsSelectUI to be able to select files again with click on the row and only submit selected files.
Also change Et2Widget.iterateOver and legacy et2_widget.interateOver to be called with new web-component classes like Et2Checkbox. Also make Et2Widget matching all widgets by default like et2_widget.
Remove legacy et2_widget_checkbox code.
Much easier to customize, though not without its issues:
- Lion give us some stuff to handle validation, forms & input that I haven't looked into
- Slightly different mixin structure, I might be missing out on something
- Properties in extending class cause TypeScript error, but still work
- Add but comment out decorators plugin so we know about it, but don't use it yet
- Better instanciation of button image node
- Remove previous mixin experiments
- Start on trying to get click handler parsing & working
