Feature Request: Detect failed installs creating empty folders, attempt to repair/merge

[ElTipejoLoco]

butler has a propensity of leaving directories and files on disk when something causes its installation attempts to hiccup (antivirus false flags, connection errors, etc.). End users attempting the installation further tend to create new directories with enumeration (i.e.- new-game gets new-game-2 unless the latter already exists, in which it'll attempt new-game-3, and so on). This can lead to bloat which should be undesirable.

Personally, I'd like it if butler (or the itch app) could detect when this happens or has happened and trash or overwrite the contents of the directory if it deems it safe to do so without possible loss of user data. This should hopefully limit the instances where games with numbered sequels that both have had issues when attempting to install start getting confusing duplicate directories (i.e.- new-game-2, the sequel to new-game, getting written to new-game-2-2).

Somewhat related to #205.