Add dry run for delete-folder command

[erik-brink]

What needs to be done:
Add a "dry run" option for the delete-folder command. The purpose is to get a list of files that would've been deleted, but it doesn't actually delete them.

Suggestions on how to get it done:
Add a click option called --dry-run

What are the arguments for getting it done:
Provides peace of mind to the end users and might prevent accidental mass deletion