Native export from (Alaska Xbase++) preview (w/o dsListLabel or callback)

[Igor_Ferk]

I suggest to implement native export from preview Alaska Xbase++ like described in
https://blog.combit.net/blog/softwareentwicklung/08-2018/export-direkt-aus-der-vorschau/

For dsListLabel (or callback) I have to change a lot of code.
https://blog.combit.net/en/blog/development/02-2017/xbase-integration/

Regards,
Igor