[UX] Improve export selection feature

[jirafey]

Describe the bug
it should create something or what is it supposed to do?

Expected behavior

A file with the seleciton.

You have a solution?
no

UAD log
Upload the logfile generat
UAD_20220410.log
ed by UAD.

[0x192]

I acknowledge that this feature is not really user-friendly right now. A uad_exported_selection.txt file is generated in the same directory as the UAD binary.
When you start UAD it automatically selects the packages found in this file.

I'll improve the UI to display the location file and explain the feature.

[onguarde]

second this, was clicking the export multiple times, nothing happened. Took some online searching and chance to find out that it's in the same directory.