Hardcoded save path

[omerinero]

https://github.com/vexdev/amarr/blame/1de6bafb09f4753e6f3294238c3d77125d6ca514/app/src/main/kotlin/amarr/torrent/model/Preferences.kt#L129

This hardcoded path brings some problems with Radarr

"You are using docker; the Amule download client places downloads in /media/usb-luca/Downloads but this directory does not seem to exist inside the container. Check your remote path mappings and container volume configuration."

Thank you

[omerinero]

Duplicated #48