Add option to export multiple routes and tracks as individual files in a single operation

[mguryan]

Is your feature request related to a problem? Please describe.
Having spent some time getting familiar with Tracks, I frequently needed to import and export them. Selecting multiple tracks to export results in a single .gpx file with all selected tracks contained in a single file.

Describe the solution you'd like
A checkbox/option to export multiple individual tracks to multiple individual files in a single operation would enable the user to quickly save individual tracks using the existing track name, without having to select and export each track individually.

Describe alternatives you've considered
The current program works as documented.

Additional context
I'm lazy and want the software to do it for me ;)