Deleting SLP files through File Processor should be restorable

[vinceau]

Currently when "Delete files with no highlights" option is enabled, the deleted SLP files cannot be restored. This could be incredibly destructive if there was an issue like #63 where combos aren't correctly being matched. It could result in someone essentially losing all their SLP files.

We should use a package like trash to send files to the recycle bin/trash so that users can restore the files if they so wish.

Alternatively, we should add very strong warnings/prompts when a user enables that option.