subcommand to delete all binaries found in repository to avoid committing binaries to source control

[discentem]

Users of Cavorite want to avoid committing actual binaries to source control at all costs. So Cavorite should have a subcommand that deletes all the binaries that have corresponding metadata files.

cavorite delete-binaries or cavorite shrink perhaps. This should prompt for confirmation or require a specific flag to auto-confirm as this is destructive:cavorite shrink --confirm.

#29 (comment) is a prerequisite to solve this issue.

This issue is a prerequisite to resolving #122